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Book Excerpt: Reef Aquarium Fishes

Organized by family for easy reference, each profile in Reef Aquarium Fishes includes all essential care, feeding and husbandry advice. The species profiled include all available reef aquarium choices, with scores of seldom seen, rare and recently discovered species. Written by the worlds most-read, most respected expert on marine fishes for the home aquarium, The PocketExpert Guide to Reef Aquarium Fishes is a must-read for any fish enthusiasts.

About the Author

Scott W. Michael is an internationally recognized writer, underwater photographer, and marine biology researcher specializing in reef fishes. He is the author of the Pocket Expert Guide to Marine Fishes (Microcosm/TFH), the Reef Fishes  series (Microcosm/TFH), and Reef Sharks and Rays of the World (Microcosm/TFH).

Having studied biology and the University of Nebraska, he has been involved in research projects on sharks, rays, frogfishes, and the behavior of reef fishes. He has also served as a scientific consultant for National Geographic Explorer and the Discovery Channel. His work has led him from Cocos Island in the Eastern Pacific to various points in the Indo-Pacific as well as the Red Sea, the Gulf of Mexico, and many Caribbean reefs.

A marine aquarist since boyhood, he has kept tropical fishes for more than 30 years, with many years of involvement in the aquarium world, including a period of retail store ownership. He is a partner in an extensive educational website on the coral reef environment,

Scott lives with his wife, underwater photographer Janine Cairns-Michael, and their Golden Retriever, Ruby, in Lincoln, Nebraska.

Excerpt from Hogfishes (Genus Bodianus)

The hogfishes are some of the hardiest members of the wrasse family. As a whole, they are durable aquarium fish that readily accept most aquarium fare, while ignoring all live corals. Most can be kept in reef aquariums as juveniles, but as they grow they will eat worms, snails, small clams, and crustaceans. The size of the aquarium needed to harbor a hogfish will depend on the species—most small to medium-sized members of the family (i.e., those species that attain a maximum length of less than 10 in. [25 cm]) can be kept in tanks ranging from 20 to 75 gallons (76 to 285 L), while more robust species require a tank of 135 gallons (513 L) or larger once they reach adult size. They need hiding places as well as ample swimming room.

Hogfishes, unlike certain other wrasses, do not bury in the substrate, so the depth of sand in your tank is of little concern. However, several of these fishes will hunt buried prey items by blowing jets of water at the finer substrate. This predatory behavior is fascinating to watch and will also stir the upper layers of the substrate.

Spanish Hogfish (Bodianus rufus): a graphic warning about hogfish feeding habits—motile invertebrates, such as brittle stars, are likely to meet this fate. Photograph by Scott W. Michael.

Many hogfishes will not tolerate the presence of members of their own species in the same tank, but they can be kept with other members of their genus. One caution: avoid placing two similarly colored species in the same tank.
As far as unrelated species are concerned, hogfishes can be belligerent toward smaller fishes, more docile species, or those fishes introduced after the hogfish has become an established resident of the tank. The moderate- to large-sized hogfishes should be kept with fish species that can hold their own, like lionfishes, squirrelfishes, soldierfishes, smaller groupers, goatfishes, angelfishes, hawkfishes, medium-sized damselfishes, sand perches, and less aggressive triggerfishes. Adding a hogfish to an established community of aggressive fishes, however, can cause the hogfish to remain hidden most of the time and never acclimate. Of course, large frogfishes, scorpionfishes, and groupers will eat any hogfish that they can swallow whole. While the larger hogfish species simply won’t fit into the average reef tank community, some of the smaller members of this group are worthy of consideration. Choose carefully, based on size and feeding habits.

Bodianus mesothorax. Photograph by Scott W. Michael.

Bodianus mesothorax
Mesothorax Hogfish
Maximum Length: 7.5 in. (19 cm).
Aquarium Suitability: This species is generally durable and hardy, with most individuals acclimating to the home aquarium.
Reef Compatibility: Safe with stony corals. Safe with soft corals. Threat to ornamental crustaceans. Threat to other invertebrates.

Bodianus mesothorax juvenile. Photograph by Scott W. Michael.

Bodianus diana. Photograph by Scott W. Michael.

Bodianus diana
Diana’s Hogfish
Maximum Length: 9.8 in. (25 cm).
Aquarium Suitability: This species is generally durable and hardy, with most individuals acclimating to the home aquarium.
Reef Compatibility: Safe with stony corals. Safe with soft corals. Threat to ornamental crustaceans. Threat to other invertebrates.

Bodianus perditio. Photograph by Scott W. Michael.

Bodianus perditio
Goldspot Hogfish
Maximum Length: 31.5 in. (80 cm).
Aquarium Suitability: This species is generally durable and hardy, with most individuals acclimating to the home aquarium.
Reef Compatibility: Safe with stony corals. Safe with soft corals. Threat to ornamental crustaceans. Threat to other invertebrates.

Bodianus izuensis. Photograph by Scott W. Michael.

Bodianus izuensis
Izu Hogfish
Maximum Length: 4.3 in. (11 cm).
Aquarium Suitability: This species is generally durable and hardy, with most individuals acclimating to the home aquarium.
Reef Compatibility: Safe with stony corals. Safe with soft corals. Threat to ornamental crustaceans. Occasional threat to some other invertebrates.

Excerpted from the PocketExpert Guide to Reef Aquarium Fishes by Scott W. Michael. ©Microcosm/ TFH Publications. Used by permission.

Posted October 16th, 2014.

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Book Excerpt: Clownfishes and Other Damselfishes

Clownfishes and damselfishes are among the most popular aquarium species, particularly for beginning aquarists. Written by a recognized authority on marine ornamental fishes, this comprehensive guide covers topics essential to keepers of these beautiful aquatic pets including selection, feeding, water requirements, diseases, breeding, and more. Full-color photos show over 20 species of clownfish and damselfish, while sidebars, charts, and tip boxes illustrate key points to consider.

About the Author

Jeff Kurtz is a freelance writer and editor who lives in Toledo, Ohio with his wife, Melissa, and two children, Aidan and Hannah. In addition to editing the health-and-fitness publication Healthy Living News, he is the Senior Consulting Editor for Tropical Fish Hobbyist Magazine and has authored or coauthored several additional books for TFH Publications, including The Simple Guide to Marine Aquariums, The Simple Guide to Mini-Reef Aquariums, The Super Simple Guide to Landscaping Your Garden Pond, and the Saltwater Aquarium Problem Solver. An avid aquarium hobbyist for almost three decades, Jeff focuses primarily on marine fish and invertebrates but enjoys freshwater fishkeeping, as well.

Excerpt from Chapter 4: Diet and Feeding for Clownfish and Damselfish

The majority of pomacentrids that you’re likely to encounter are omnivorous. In nature, some, such as the gregories (Stegastes spp.), have a diet that includes a greater proportion of algae, while others, such as the various Chromis species, rely more heavily on zooplankton. But few pomacentrids are so specialized in their diet that they completely exclude meat or veggies. That’s great news for hobbyists because, as you might expect, fishes that have a generalized diet typically adapt better to aquarium fare and have a much better survival rate in captivity compared to specialized feeders.

The pomacentrids in general are enthusiastic, opportunistic feeders. Offer yours a wide variety of foods. Photograph by Ligo/Shutterstock.

Variety Is the Spice of Life

So, being omnivores, pomacentrids should be offered a diet that is not exclusively plant- based or exclusively protein-based. This is very easy to do nowadays, as the selection of fresh, frozen, dry, and freeze-dried aquarium foods available to hobbyists has never been better.

Your pomacentrid menu should include items such as a staple pellet or flake, spirulina pellets or flakes, frozen mysid shrimp, frozen formulas for both omnivores and herbivores, and, at least occasionally, fresh meaty foods of marine origin, such as clams, shrimp, scallops, and fish, chopped to fit the mouths of pomacentrids.

Crazy Over Clams

Though it’s the rare pomacentrid that won’t start feeding shortly after purchase, it can sometimes take a day or two to get some specimens interested in eating. This is nothing compared to some marine fishes, such as certain butterflyfishes, which may take several days or even a week or more of coaxing with foods of all sorts before they’ll deign to accept anything you offer, but, nonetheless, it can be disconcerting when a clownfish or damselfish ignores your offerings. In such cases you can almost always win over a picky pomacentrid with chopped fresh clams. In fact, there’s just something about the scent of fresh clam in the water that really rings the dinner bell for almost any marine fish.

Shucking the fresh clams and chopping the meat is a bit labor-intensive, but you’ll find that it’s well worth the effort. Make sure the clams you purchase are still alive. Choose only those with their shells clamped tightly shut. Skip any that have gaping shells or an off odor, as they are either dead or dying. I usually buy a large quantity of clams, shuck and chop them all at once, set some of the fresh meat aside in the refrigerator to feed over the course of a few days, and freeze the rest for future use.

I prefer to freeze chopped clams in serving-size batches, so I usually dole out equal-sized portions of the meat into an ice-cube tray. That way, whenever I want to offer my fish a nutritious treat I simply pop one of the servings out of the tray, thaw it, drop the bits into the tank, and watch the fish go crazy!

Cyclops for Small Mouths

A great food to use when trying to elicit an initial feeding response from smaller pomacentrids, especially those that feed on tiny zooplankton in nature, is frozen cyclops. Cyclops is a popular item for feeding sessile invertebrates in reef systems, but I’ve found that most pomacentrids can’t resist them either.

When feeding very small foods such as cyclops, it’s helpful to temporarily shut down your filtration and water pumps so there is no water movement. It doesn’t take much force to suck these tiny crustaceans into a sump overflow or filter intake or to scatter them all around the aquarium so the fishes never even notice them. But if they are concentrated in one area and allowed to sink slowly to the bottom, they’ll get the attention of your fishes and it won’t take long for them to start snicking up these minuscule morsels. A little goes a long way when you’re using cyclops, so be careful not to overdo it!

Incidental Veggies

If your clownfish or damsel happens to share an aquarium with a herbivorous fish, such as a tang or rabbitfish, there’s an easy way to make sure your pomacentrid gets its greens. That is, provide the tang or rabbitfish with a sheet of dried marine algae, such as sushi nori or red or brown marine algae, to nibble on each day. Pomacentrids generally won’t tear algae off the sheet, but they will gladly snap up the tiny bits that float around in the water column after the tang or rabbitfish rips into the sheet.

Tasty Tidbits Crawling in the Tank

Though it’s not necessary to feed live foods to pomacentrids, they will certainly appreciate and benefit from eating them, and there are various ways—short of actively culturing them or buying them in small, cost-ineffective batches from your local dealer—to provide an ongoing supply of nutritious live foods that your clownfish or damselfish can nibble on.

Aquascaping your tank with copious quantities of quality live rock is one way to introduce populations of these edible organisms. As your system matures, all sorts of little critters will hatch out from the rocks, such as pods—amphipods and copepods—various worms, mollusks, and echinoderms, and clownfishes and damselfishes will gladly gobble up many of them.

Installing a live-sand substrate—or seeding a non-live sand bed with a small quantity of live sand to get the populations started—also is a good way to enhance the microfauna in your system.

Live rock provides clowns and damsels with myriad small organisms upon which to browse. Photograph by Iggy Tavares.

But perhaps the best way to provide a steady supply of live foods for hungry pomacentrids is to connect some form of refugium to your aquarium. A refugium is essentially a vessel that is separate from your main aquarium but shares the same system water (water is drawn from the display tank, flows through the refugium, and is then pumped back into the display tank). A sump or aquarium of any size can be converted for this purpose. You can also choose from the various commercially manufactured hang-on-tank refugia that are available on the market.

As the name suggests, a refugium provides a safe haven, or refuge, for organisms that would be either eaten or harassed in your display tank. These organisms could include the aforementioned amphipods, copepods, and other desired microfauna, as well as fishes or invertebrates that have been injured or are the target of territorial aggression. Because they are isolated from predators and tormentors, organisms kept in the refugium have the opportunity to reproduce more abundantly than they could in the display tank or to recover from tankmate-inflicted injury.

By placing some pieces of quality live rock and/or a bed of live sand in the refugium, you can establish healthy populations of edible microfauna. As these populations grow, some of these little organisms, along with their eggs and larvae, will be carried into the display tank, where the fish can gobble them up. Those that avoid being eaten will help to establish populations in the main tank, thereby increasing the overall biodiversity of the system.

I should add that many hobbyists also grow various forms of macroalgae, such as Chaetomorpha spp. (a.k.a. “chaeto”) and Gracilaria spp., in their refugia for the purpose of nutrient export. These algae take up dissolved nutrients, such as nitrate and phosphate, from the water, and the aquarist routinely harvests a portion of the algae, thereby removing the nutrients from the system. So, in addition to providing an ongoing smorgasbord of pods, worms, and other tiny critters, a refugium can help to keep your aquarium’s water quality at its best.

Should You Feed Live Foods?

Of course, live foods, such as mysid shrimp and newly hatched and adult brine shrimp (preferably enriched by feeding with a vitamin supplement), will be accepted with gusto by clownfishes and damselfishes and can certainly be offered as an occasional treat. However, with the variety of high-quality prepared fish foods on the market today, it’s really not necessary to offer live foods to pomacentrids on a routine basis. An exception must be made if you decide to breed clownfishes, as the larvae must be fed live marine rotifers and newly hatched brine shrimp, but we’ll get into that in greater detail in Chapter 8.

Whatever you do, try to avoid getting too lackadaisical in your feeding, for instance by relying too heavily on only one dry or frozen food for your own convenience.

Kicking Up the Nutritional Value of Your Pomacentrid’s Repast

Offering a varied diet is the best way to ensure that your clownfish or damselfish isn’t missing an important element in its diet, but as added insurance against dietary deficiencies it’s a good idea to occasionally enrich your pomacentrid’s food with a nutritional supplement.

Soaking dry or frozen foods with one of the liquid supplements that are available on the market (most contain important vitamins and highly unsaturated fatty acids, or HUFAs) prior to feeding them to your fishes will help to enhance the nutritional value of the foods, which, in turn, will keep your fishes healthier, more colorful, and better able to recuperate from injury or illness. These products can also be fed to live foods—such as brine shrimp—in order to enhance their nutritional value by adding them directly to the water in the culture container.

Excerpted from the Aquarium Success Guide to Clownfishes and Other Damselfishes: The Complete Guide to the Successful Care and Breeding of these Hardy and Popular Marine Fish by Jeff Kurtz © TFH Publications. Used by permission.

Posted July 6th, 2012.

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Book Excerpt: Tetras and Barbs

Tetras and barbs are a mainstay of the tropical fish hobby. Most people keep a community tank, and most community tanks rely heavily on tetras and barbs for color and action. Until now, however, there has not been a definitive book that covers these popular species exclusively. This book answers that need. Written by a recognized leader in the field of keeping and breeding tetras and barbs, the text provides a good overview of the care for these aquatic gems.

 About the Author

Since entering the hobby in 1989, Randy Carey has been keeping and breeding all types of small, soft-water fishes, but he specializes in the scatterers (tetras, barbs, danionins, rasboras, etc.). His aquaria room is lined with seventy-plus aquaria that span the roles of display, breeding, and various auxiliary uses. As an active member in the Minnesota Aquarium Society he is the first to attain the club’s Lifetime Award, earned by his breeding accomplishments.

Randy established one of the first aquarium web sites (Randy’s Fishroom in 1996) and probably the first aquarium blog (1997-2004). Since 1999 he has contributed a column, several feature articles, and photos for the pages of Tropical Fish Hobbyist Magazine. When traveling across the United States and Canada for speaking engagements, he delivers advanced topics to aquarium societies and tailors common-interest presentations when addressing non-aquarists. Randy maintains this book’s support site at

Excerpt from Chapter 2: Tetras and Their Relatives


Spanning so many species and lineages, the tetras also span many shapes and sizes: from the disk-shaped silver dollars to the extremely elongated Iguanodectes, and from the miniature amber tetra (Hyphessobrycon amandae) to the large pacu and piranha. No one color pattern or set of markings visually defines the tetras. Yet they do share some finnage features.

The caudal fin is forked into an upper and lower lobe. The fishes possess a single dorsal, which is short (front-to-back, where the fin runs along the body). An adipose fin is almost always present. But these features are common, not distinguishing, throughout all characins and (aside from the adipose) also most cyprinids.

The finnage that best distinguishes the tetras is the long anal fin. Typically it begins under or just behind the dorsal fin and runs almost up to the caudal. Classic examples are worn by the black tetra (Gymnocorymbus ternetzi), bleeding hearts, all Hyphessobrycon, silver dollars (Metynnis), and so many others. While this long fin is a signature feature centered in the tetras, it is represented in a few families closely related to Characidae: strongly present in the closely related hatchetfishes, and less long but still observable in the African tetras (Alestidae) as well as in Cynodontidae and Acestrorhynchidae.

Aquarium Strategies

Most tetras are quite similar regarding their aquarium care. However, three of the tetra subfamilies (Characinae, Serrasalminae, Bryconinae) vary enough that we must adjust our strategies accordingly.

Core Tetras

These are the fishes that have stereotyped tetras as relatively small and peaceful. They provide the lively movement in the middle strata of the aquarium. With nature offering literally hundreds of species, one can find a wide variety of colors on varying body shapes. Some of the most intense colors are found in this group: cardinal tetra (Paracheirodon axelrodi), serpae tetra (Hyphessobrycon eques), lemon tetra (Hyphessobrycon pulchripinnis), and blue king tetra (Inpaichthys kerri). These tetras also provide some of the best schooling fishes (such as neons and rummy-noses) as well as dramatic group/pack behavior (the various rosy tetra species). Tetras are not loners, so each species that is displayed should be represented by several specimens—never singly or even as just a pair.

The core tetras include some of the most brightly colored species, such as the lemon tetra (Hyphessobrycon pulchripinnis). Photograph by MP. & C. Piednoir.

If your goal is for a simple display with just a single species, select tetra species that contribute some dramatic feature: color, finnage, tight schooling, or intense pack behavior. I’ve seen an aquarium show entry stocked only with a school of the intensely blue Inpaichthys kerri that was so impressive that it won the coveted “aquarium beautiful” award.

If you are planning a community of several species, plan the species selection to provide visual contrast among the various tetra species by varying color, body shape, finnage, and behavior.

If the lower level- and bottom-dwelling fishes, such as catfishes or cichlids, are the showpiece specimens in your aquarium, you may want the mid and upper levels occupied by background fishes. This role can be filled by tetras with subtle coloring and that school loosely (instead of schooling in synchrony or interacting as a pack).

Provide significant aquascaping to relax the fish and to provide temporary refuge. Plants, in particular, will draw out the natural behavior and strong colors that are otherwise muted in captivity. Likewise, most tetras show their best color in water that is soft (6 dH or less) and slightly acidic (pH 5.5–6.8). Many of the tetra species come from blackwater streams, and these welcome more extreme conditions: 1–2 dH, pH 4.5–6.0.

As a general rule, the core tetras do not eat plants. Flakes should complement any tetra diet, but they do prefer meaty foods, be they frozen or live. Tetras eagerly attack small live foods like fruit flies, mosquito larvae, blackworms, and brine shrimp.

Characinae: Scale Eaters

The dentition and gut contents identify many of the Characinae as scale eaters. Yet aquarists have successfully kept other aquarium fishes with several of these species. Perhaps success is attributed partially to keeping them well fed—nature studies reveal that scale eating increases as food supplies decrease. If you give them tankmates, keep them well fed and make sure the other fishes are not smaller. Keep a watchful eye on the tank’s social dynamics and take action as needed.

Bucktooth tetra (Exodon paradoxus). Photograph from TFH Archives.

Serrasalminae: Pacus, Silver Dollars, Piranhas

The fishes of this tetra subfamily are larger and have extreme feeding habits compared to the core tetras. The large pacus—two to four feet (60 to 120 cm) long or more—are vegetarians and outgrow a 55-gallon (200-liter) tank within their first year. If you must keep these fishes, prepare for a multi-hundred-gallon aquarium designed without plants. In contrast, the silver dollars are 4 to 6 inches (10 to 15 cm) long. Their sizable disk-shaped bodies adorned with bright, silvery scales is eye-catching, making them popular and showy fishes. Their diet is mostly vegetarian, so plants seldom survive within their aquascape. Finally, the over three dozen species of the infamous piranha are sizable (typically six to ten inches, 15 to 25 cm), most should be kept in a group, and they require very large tanks. Typically they are kept in a species tank to display their attitude and feeding behavior. Aquarists have had mixed results when keeping them with other fishes, and failures seem to involve underfeeding.

Myleus rubripinnis. Photograph from TFH Archives.

Bryconinae: Brycons

These sizeable trout-like fishes are more important as food than as aquarium inhabitants. Most are unremarkably silver and large (6 inches to over 2 feet, 15 to 60 cm). Resigned to a background presence if used in aquaria, they arguably serve best as dithers or targets for larger fishes.

Triportheus albus. Photograph by Aaron Norman.

Excerpted from the Aquarium Success Guide to Tetras and Barbs: A Complete Guide to the Successful Care and Breeding of the Two Most Popular Groups of Aquarium Fish by Randy Carey © T.F.H. Publications. Used by permission.

Posted January 10th, 2012.

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Book Excerpt: The Simple Guide to Freshwater Aquariums

The Simple Guide to® Freshwater Aquariums (Second Edition) is the key to becoming a dedicated aquarium hobbyist is to succeed with your first aquarium. The Simple Guide to® Freshwater Aquariums concentrates on providing you with a complete plan and all the information you need to choose and use the right-for-you aquarium equipment and the right-for-you fish and plants: it wants you to succeed. The information is presented in a completely straightforward text that’s easy to read, easy to understand – and very definitely easy to put to good use.

About the Author:

David E. Boruchowitz is in his sixth decade of fishkeeping. He wrote and edited for T.F.H. Publications for more than a decade and has authored a large number of books on a variety of topics. He also served as Editor-in-Chief of Tropical Fish Hobbyist Magazine.

Excerpt from Chapter 5: What Options Do I Have?

Hang-On Outside Filters

The hang-on outside filter is the most popular and versatile design, and it’s the one I recommend for your first aquarium. This filter has undergone a lot of improvement since the early air-driven models, which were nothing more than a box filter hanging on the back of the tank. They were fed with siphon tubes, and an airlift returned water to the tank through the filter medium. Modern power filters use a water pump to draw water up from the tank and into the filter, where it flows through chambers of filter media and returns by gravity overflow to the tank.

Although there are models available that contain chambers into which you can heap the filter media of your choice, most filters today have modular filter components that you can mix and match and slide into the filter sections. That makes it much easier to service the filter, and it also ensures that water will not find its way around the media instead of going through them, since the medium cartridges fit snugly into the compartments.

Usually a particular filter is available in a series of sizes, each successive one being both larger (and thus having more room for media) and more powerful (in having a stronger pump that delivers more gallons per hour). The idea here is that you can buy a filter sized to your particular aquarium. My suggestion is that you ignore such advice and choose one of the largest models. What?

First of all, you get more filtration for your dollar with the larger ones. Second, if you later upgrade to a larger tank, the larger model may still be adequate. Third, there is basically no such thing as too much filtration. An absolute minimum would be a unit that delivers a flow rate of five or six times the tank volume per hour, but ten times is even better. This is mainly because of biofiltration—more flow means more bacterial contact with more oxygenated water. It also improves the aeration of the water, making sure oxygen levels stay at optimum levels for the fish throughout the tank.

Last but not least, the ratings on most filters are nearly useless. Typically you might see something like “for aquariums of 10 to 60 gallons.” A filter truly adequate for a 60-gallon (230-liter) tank would have a flow rate that would overpower a 10-gallon (40-liter) tank. Although I said that it’s not possible to over-filter a tank, you also do not want the flow rate to be so powerful that it creates a whirlpool effect, with the fish being whipped around the tank all the time. The real problem, however, is that it is unlikely that the filter actually has an effective flow rate of 300 gallons per hour (gph), making it unsuitable for a 60-gallon tank. But even the gph rating can be misleading. The filter’s pump may be rated at, say, 150 gph, but that doesn’t mean that 150 gallons go through the filter every hour. Just pumping the water through the empty system will cut down on the flow; even the introduction of new media will reduce the flow, and as the filter gets dirty the flow decreases even more.

So what do you do? The solution is to buy the biggest and most powerful power filter you can. If you can hang it on the tank, it’s probably not too big. I have very successfully used a spare 400-gph filter on a 20-gallon tank; when I no longer needed it there, the filter went back on a 55-gallon tank. The filter was slightly narrower than the back of the tank on which it hung, but it worked very well. An even better idea is to get two power filters, each big enough to handle the tank alone. Not only does this give you greatly improved filtration and aeration, but it also provides a backup if one filter suddenly breaks down, and it permits you to clean them on an alternating schedule, minimizing the loss of biofiltration capacity. Remember, there’s no such thing as overfiltration, only underfiltration.

Canister Filters

Canister filters have some superior characteristics, but they are the most expensive way to go. One of their preferred characteristics is that they can be placed away from the aquarium (usually under it) and are connected to the tank by hoses. This means that the tank can be placed almost flush against the wall, since there only needs to be enough room for a couple of pieces of tubing behind it.

The major filtration advantage canister filters provide is that the water flows through them under pressure. This is because the filter is a closed system. Water is drawn from the tank and then flows into the filter, through the media, and back to the tank. It is driven by a water pump that, depending on the particular design, is either integral with the filter canister or plumbed into the system. This means that considerable power can be generated, which in turn means that the water is forced through the media under pressure, providing maximum filtration benefits. This also permits in some models the use of diatomaceous earth (a powder made up of diatom skeletons) as a filter medium; water will not really flow through it, but it can be forced through it under pressure. Diatomaceous earth filtration is meant as a temporary filter to “polish” the water—the diatomaceous earth cartridge is replaced by a regular mechanical medium for full-time use.

Canister filters work well and are excellent for large aquariums. They don’t do much that a couple of high-power outside power filters can’t do, but they are very efficient filters, and many aquarists prefer them, despite their complexity.

Most of that complexity is simply plumbing, since you have to get water from the tank to the canister and back again. There are many options in how you set up a canister filter, which is why some of them do not include fittings, which have to be purchased separately. Fortunately, the major brands currently on the market all include fittings and tubing. Many canister filters have several options for the return, from simple tubing outlets to spray bars that diffuse the return flow over the entire surface of the tank.

Whatever filter you choose, if it does not have a true wet-dry option, you should use a sponge filter, add-on rotating contactor, or other biofilter in addition to it.


Recently “wet-dry” filters have enjoyed greater popularity for use with freshwater aquariums, although they have always been used mainly for marine aquariums.

Just what is wet-dry, anyway? Well, obviously, if filters are filtering aquarium water, they cannot be dry, but the name makes sense because these filters make use of a medium that is kept moist but not fully submerged in water. This is the “dry” part of the filtration process.

The purpose of this type of medium is to increase biofiltration, which it does significantly, because air has much more oxygen in it than the most highly oxygenated water does. With the vastly improved oxygen supply, many times the number of bacteria will grow in a given area, and they will process wastes at a much greater rate.

The design of wet-dry filters is quite varied, but they share the feature that somehow water is dripped, splashed, sprinkled, trickled, or sprayed onto a high-surface-area medium, through which it percolates before returning to the tank. Some power filters incorporate a wet-dry section as the final stage, but there are also some that claim to do so and don’t.

Excerpted from The Simple Guide to® Freshwater Aquariums (Second Edition) by David E. Boruchowitz. © T.F.H. Publications. Used by permission.

Posted December 16th, 2011.


Book Excerpt: Lionfishes and Other Scorpionfishes


Aquarium Success: Lionfishes and Other Scorpionfishes The venomous but beautiful scorpionfishes are extremely popular among home aquarists, with many species readily available in pet and aquarium stores. Written by one of the leading experts on this group of fish, this exclusive guide is the only trade book on the subject and covers topics essential to ensure a healthy and thriving tank, highlighting the top 25 species with profiles of their natural range, size, behavior, aquarium suitability, and specific care requirements.

About the Author:

Frank C. Marini III, PhD, born and raised in Hudson, Massachussets, is a long time fish nerd. Working as a stem cell biologist by day, Frank’s passion for keeping scorpionfish and their kin has lasted more than 30 years. His scientist side affords him a unique perspective into animal behavior, and his fish nerd side keeps him curious and motivated to find the keys to unlocking successful long-term husbandry of these remarkable fish. In 1995, Frank was credited with the first successful breeding of Banggai cardinalfish in captivity, and his writings have inspired thousands of fishkeepers to delve into marine fish breeding. For the past 15 years he has bred many species of marine fish, and accompanying this, he has moderated web forums on fish breeding and keeping aggressive and predatory fish in the home aquarium. Frank can be contacted at

Excerpt from Chapter 1: Scorpion Biology

Distribution and Habitat

Lionfishes and scorpionfishes are widespread in the world’s oceans but are primarily found around coral reefs. Man has aided lionfish distribution over the past 50 years, with Pterois miles entering the Mediterranean Sea from the Red Sea via the Suez Canal. Also, P. volitans and P. miles were introduced into the Atlantic Ocean along the U.S. East Coast and have become established there. Scorpions are found in water depths ranging from 2 to 1260 feet (less than a meter to 380 meters), on hard and soft bottoms, coral reefs and artificial substrates (e.g., sunken ships or oil rigs). In corals reefs and rocky outcrops, the fish hide in caves and crevices and underneath rock overhangs. Many small scorpionfishes live among the coral rubble, while some larger forms lie in exposed areas waiting for passing food. Many species are well camouflaged, as they are replete with dermal appendages, muted color tones, and skin flaps and tassels that allow them to disappear from plain sight. A sedentary lifestyle enhances their ability to blend in and ambush unsuspecting passers-by.

Biological Features

Scorpaeniforms have many adaptations in anatomy and behavior that serve them well in the wild, adaptations that must be taken into account when keeping these animals in captivity.

Ecological Role

Easily outpaced by other animals, scorpionfish and lionfish are slow-moving hunters. Lionfish tend to appear conspicuous, so they rely on their unusual colorations and fins to discourage potential predators. On the reef, lionfish are top predators, as they are active hunters who ambush their prey using outstretched fins to slowly herd and corner their prey. As for scorpionfish, their strategy is different. They are extremely stealthy and sedentary, often sporting camouflaging coloration, feeding on prey that comes too close.

Their hardiness, graceful movements, and stunning appearance have made lionfish extremely popular in the marine fish hobby—in spite of their venomous spines.


Lionfish are active predators of smaller fish, crabs, and shrimp. They move by slowly undulating the soft rays of the dorsal and anal fins, stalking and cornering prey with outstretched, expanded pectoral fins. Their kill shot is a lightning-quick snap of the jaws, swallowing their prey whole in an instant. In the wild and in captivity, these fish can be cannibalistic. Lionfish appear mostly nocturnal, given their tendency to retreat to hiding areas during the day. However, in captivity we clearly observe lionfish feeding throughout the day, indicating that in the wild recently fed individuals may merely be retreating to their hiding spot after eating.

Most scorpionfish remain motionless for hours, relying on concealment to aid in ambushing their prey and feeding whenever the opportunity arises. On the reef, they feed on a few organisms a day, although large scorpionfish may ingest only one larger prey every few days. Scorpionfish diets vary, with some large scorpionfish feeding exclusively on fish. Others of similar size demonstrate a wide dietary breadth, feeding on shrimp, crabs, and squid in addition to fish. Many small scorpionfish feed almost exclusively on small crustaceans and worms. Like lionfish, scorpionfish tend to hunt mainly at twilight—they’re crepuscular hunters—but they never pass up a meal opportunity, day or night.

Prey Capture

The cavernous mouths of many scorpaeniform fishes are disproportionately large compared to their body size, so they are able to take even very large prey. Prey capture takes place in three phases: 1) orientation to the prey item, 2) seizing the prey (expansion and compression of the mouth) and 3) manipulating and swallowing the prey. When a scorpionfish sees a prey item, eye movements indicate the scorpionfish is tracking the prey. The scorpionfish raises its head slightly, visually orienting toward the prey’s eyes. They attempt to orient their bodies toward the prey’s head. This adjustment precedes the fish’s rolling and pitching its pectoral fins to ensure the prey is within range.

Just before opening its mouth, the fish depresses its mouthparts, essentially spring-loading the mouth structures with potential energy to explode wide open for the strike. Bony fishes in general have similar mouth expansion biomechanics, but in scorpaeniforms mouth movement is so rapid that it creates a large lateral expansion, resulting in additional suction. The fish literally sucks the water surrounding the prey into its mouth, rendering the prey as powerless to resist as a surfer on a bad wave. Once the prey is in its mouth, the fish holds it securely with its curved conical teeth, frequently manipulating the prey with abbreviated mouth expansion and closure—in essence, readjusting the food item to ensure it is head first. Swallowing occurs with a raking motion of the throat teeth. This entire process occurs swiftly—complete prey capture has been recorded at 45 milliseconds for a stonefish, with mouth opening and closing occurring in under 20 milliseconds (Grobecker, 1983).

Scorpionfish are cryptic and sedentary relatives of the lionfish. This one is well camoflaged in a barrel sponge waiting for unsuspecting prey.

Defensive Behavior

Many scorpions rely on their cryptic coloration and sedentary nature to fend off predators. By being completely camouflaged, they rely on hiding in full view as a passive defense. Many have specialized body shapes and possess skin tassels that allow them to appear convincingly identical to algae tufts, rockpiles covered in sponges, or unpalatable crinoids. To supplement the camouflage, some scorpions mimic the undulating movement of local algae or debris; this is done, for example, by the leaf scorpions, whose bodies rock side-to-side, mimicking the wave action of local plants. However, if a predator stumbles across or threatens a scorpaeniform, the fish reacts. Initially it may flee, quickly settling into a new area, then quickly freezing again, remaining motionless. Alternatively, a few species possess brightly colored fin markings that are usually held in the closed, or darkened, position, such as on the bottom of the pectoral fin. These markings, called flashes or flasher fins, are rapidly exposed at a threat and may serve as a warning. Alternatively, the bright color flash may confuse or disorient predators.

Certain scorpaeniforms get their common names (stingfish, waspfish, etc.) from their ability to defend themselves with a venomous sting, although it’s used as a last-resort defensive weapon to prevent a repeated attack. Venom glands at the base of certain spines produce a venom that the fish injects via the spines. The venom immediately causes severe pain that just about guarantees a hasty retreat of the threat. Medical and scientific journals have documented numerous cases of human envenomation, and I’ve dedicated a whole section to this topic later in this chapter.

Multifocal Lensed Eyes

Lionfish eyesight consists of a multifocal optical lens in each eye, with a short focal length (Karpstam, 2007). Long focal lengths equate to high optical magnification of the image and low light-gathering ability, meaning they can see farther but require hunting during daylight hours, whereas short focal lengths correspond with higher light-capturing ability and less magnification of the target, meaning more evening time hunting of prey that swims nearby. Because lionfish possess eyes better suited for their crepuscular behaviors, they strike at food from short distances and do more low-light hunting.


Scorpaenids have many small teeth located on the upper and lower jaws in densely packed bilateral clusters, and in a small patch on the anterior roof of the mouth. These teeth appear functionally limited to grasping prey captured by the extraordinarily quick predatory strike. The pharyngeal (throat) teeth help them secure and swallow their meals.


Many scorpaeniforms lead an extremely sedentary lifestyle, and marine organisms (algae, hydroids, and bacteria that settle from the water column) can attach to them. Because of this, many have evolved a protective coating, called a cuticle. A cuticle is a thin white or opaque skin covering encasing the entire animal. The fish shed this cuticle to rid their bodies of these organisms. Some species, like Rhinopias, shed this cuticle weekly, and many others, such as lionfish, shed monthly or even less frequently. Shedding can take minutes to hours. Shedders shake their body rapidly until the cuticle tears off in small pieces. In home aquariums, cuticle shedding looks unsettling. In a lionfish, you’ll notice that the fish darts and dives, then convulses for a few seconds; a white, ghost-like tissue appears in the water. The cuticle protects the fish from illness, and excessive cuticle shedding indicates poor health, as they increase cuticle shedding during protozoan infection as a way of reducing their exposure.


Few published records of natural predators of scorpionfish and lionfish exist. One short report suggests that the piscivorous cornetfish Fistularia commersoni is a predator of Pterois miles. Judging by the presence and reverse orientation of a partially digested specimen of P. miles in the stomach of a large F. commersoni, the authors concluded that cornetfish may ambush lionfish from the rear, consuming them tail-first, allowing the venomous spines to fold harmlessly forward. In the home aquarium, venomous spines aren’t a deterrent to larger piscivores, as I’ve personally witnessed antennariids (frogfish and anglerfish) consume small lionfish. Additionally, other scorpions readily consume smaller ones. I have watched in horror as my large P. volitans engulfed two juvenile conspecifics. It is likely that natural lionfish predators include sharks, as many sharks consume noxious organisms without displaying ill effects from the poisons.

Social Structure

Lionfish are often seen moving about during the day, alone and in groups of two to six animals. They may live alone most of their lives, fiercely defending their home ranges from other lionfish. As juveniles, lionfish aggregate into small groups, and this cooperation probably increases their ability to gather food. During the spawning season, adult lionfish also may gather into groups, with males acting more aggressively than females. In many lionfish no clear sexual dimorphism or dichromatism exists—however, clear demarcation between sexes exists in Dendrochirus brachypterus, the dwarf fuzzy lionfish. Lionfish reproduce like many other fish, producing eggs that are fertilized outside the female’s body. There is little information about the social structure of most reef-dwelling scorpionfish species. Most observations about these fishes are from anecdotal reports from scuba divers and aquarists keeping them. We do know that most tropical species remain solitary, with occasional sightings of scorpionfish pairs, and the leaf scorpionfish have been noted in pairs and trios.

Excerpted from Lionfishes and Other Scorpionfishes: The Complete Guide to the Successful Care and Breeding of These Spectacular and Popular Marine Fish by Frank C. Marini, Ph.D. © T.F.H.  Publications. Used by permission.

Posted November 23rd, 2011.

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Nature Aquarium: Complete Works 1985-2009 By Takashi Amano

Nature Aquarium: Complete Works 1985-2009 By Takashi Amano

Nature Aquarium: Complete Works 1985-2009 takes you on a journey through over two decades of the most innovative and breathtaking designs from nature aquarium pioneer Takashi Amano.  In this collection of works from the world-renowned aquarist, over 200 vibrant, full-color photos display the captivating beauty of nature aquariums while providing detailed, step-by-step instructions on how to create your own aquatic masterpiece.  Along with expert advice on plant and fish selection, water chemistry, and maintenance, the author includes essays outlining aquarium aesthetics and his own personal design philosophies to inspire readers to create their own harmonious and tranquil nature aquarium designs.

Amano Image

The Real Pleasure of Keeping Discus in a Large Aquarium

Although the vividly colored hybrid discus is attractive, the wild original species also has a big appeal. Generally speaking, the wild strain is more timid than its artificially bred hybrid counterpart.  It tends to calm down better if an aquarium offers driftwood and aquatic plants where it can seek refuge. It becomes accustomed to a new environment and settles down more quickly if its environmental condition is kept as similar to the natural habitat as possible. For this reason, Nature Aquarium created in a large aquarium is more suitable for wild discus.   However, keeping discus in a layout has its own difficulties.  When a discus is introduced in an aquarium at first, it hides behind driftwood and does not come out to swim gracefully in an aquarium. Under such conditions, its body color darkens to blend into the shade. Although feeding can sometimes be effective for getting it acclimated to the aquarium environment as quickly as possible, it does not take well to artificially prepared food initially.  It may be necessary to devise some special measures to entice them, such as giving some bloodworms along with prepared food at the risk of fouling water, or putting other fish in the aquarium in the hope that discus will follow them to come out of hiding. After overcoming many difficulties and becoming accustomed to the aquarium environment, a discus not only graces the aquarium by regaining its beautiful colors, but it also starts to show its natural behaviors, such as spawning on driftwood. That will greatly add to the joy of keeping this fish. The real pleasure of keeping wild discus in Nature Aquarium is to bring out their natural beauty and behaviors by perfecting the habitat environment in an aquarium.

Excerpted from the book Nature Aquarium: Complete Works 1985-2009 by Takashi Amano (pgs. 56-57).  ISBN: 9780793806492. ©2011 TFH Publications, Inc.  Used with permission.

Posted December 14th, 2010.

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