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A 10-Gallon Coral Garden

Photograph by Sabine Penisson.

By Sabine Penisson

The March 2013 issue features a 10-gallon reef tank that has been in operation for 3½ years. It is lit with a homemade LED fixture and has a hang-on-the-back filter filled with a mini pocket of activated carbon and filter floss. A 10 percent water change is conducted twice a week and the floss is also changed twice weekly.

In terms of livestock, the tank only features seven fish: one Okinawa goby (Gobiodon okinawae), a pair of greenbanded gobies (Elacatinus multifasciatus), one bluestripe pipefish (Doryrhamphus excisus), a ring-eye pygmy goby (Trimma benjamini), one blackbelly goby (Eviota nigriventris), and shrimp goby (Stonogobiops yasha). The  shrimp goby lives with two shrimp (Alpheus randalli) partners. The fish are camera shy but gluttonous! The tank holds an anemone crab (Neopetrolisthes oshimai)who has chosen the large and chubby Trachyphyllia geoffroyi to live in.

The reef is strongly large-polp stony coral oriented.Several morphs of AcanthastreaMicromussa, and Caulastrea take most of the space, but photosynthetic Caribbean gorgonians, a piece of Euphyllia paraencora, and various nicely colored softies complete the setting. It is a rich and mature nano tank, which has never had any major issues, and is filled with lively and sympathetic creatures!

For more on setting up a successful coral garden of your own, check out this month’s “Going Nano” column.

Posted February 7th, 2013.

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February 2013 Calendar

Tropical Fish Hobbyist’s February 2013 Desktop Calendar is now available!

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Visit the Web Extras section of for additional downloads, videos, and much more!

Posted February 1st, 2013.

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2012 International Aquatic Plants Layout Contest

The February 2013 issue featured the top 12 winners of the International Aquatic Plants Layout Contest. The contest ranks the best aquascapes from around the world. Here we feature an additional 14 high-ranking entries.

World Ranking #13

Su En Zong


Title: Scenic Stone Forest

Dimensions: W120 x D60 x H50 cm (W50 x D25 x H20 inches)

Evaluation: This is an iwagumi layout, which reminds one of scenes of “Guilin” or “Zhangjiajie,” known for their Karst topography in China. It seems even the height and arrangement of stones are meticulously calculated. Although the usage of aquatic plants is unique, and they grow nicely, it would be difficult to maintain this beautiful condition for a long period. This point could be a drawback of this layout.

World Ranking #14

Robertus Hartono


Title: Reaching

Dimensions: W90 x D45 x H45 cm (W35 x D25 x H25 inches)

Evaluation: The layout consists mainly of stones, and some trees made with driftwood and mosses are arranged inside the aquarium. This kind of expression is a very common layout style. But the image of trees reminds us of pine trees, taking roots in a steep rock mountain, and this became a unique way of expressing natural feel in the aquarium layout.

World Ranking #15

Timucin Sagel


Title: Stairway to Heaven

Dimensions: W100 x D60 x H45 cm (W40 x D25 x H20 inches)

Evaluation: This layout looks like a picturesque scenery or a stage setup and leaves a unique impression. The layout does not look like natural scenery, but an artificially created landscape. It is not easy to make a grading for such a layout, but it seems the beauty of the whole layout and the appeal of composition are accepted favorably by juries.

World Ranking #16

Bernice Sim


Title: Elusive Plateau

Dimensions: W100 x D45 x H45 cm (W40 x D20 x H20 inches)

Evaluation: The creator succeeded to make a powerful layout by placing a large stone in the foreground. The simple foreground covered by cosmetic sand also emphasized the existence of stone. The white sand, extending to the background, is also effective in emphasizing perspective in the layout. The position of fish is also good.

World Ranking #17

Hidekazu Tsukiji


Title: A Hill with Sweet-Scented Wind

Dimensions: W120 x D45 x H45 cm (W50 x D20 x H20 inches)

Evaluation: What attracts the eye to this layout is the expression of driftwood integrated with stones. By coordinating the stone arrangement with driftwood shape, the creator tried to express a sense of unity, using mosses and Hygrophila pinnatifida. The composition and aquatic plant condition are also good.

World Ranking #18

Luis Carlos Galarraga


Title: Apnea

Dimensions: W120 x D45 x H45 cm (W50 x D20 x H20 inches)

Evaluation: This is a typical Nature Aquarium layout style without any eccentric rendering. Perspective is created by arrangement of stones and planting design. The position of fish, as well as layout composition and open space, play an important role of making a stage effect of water flow. This is a high-level layout, meticulously designed in details.

World Ranking #19

Leandro Artioli


Title: Unknown Way

Dimensions: W60 x D30 x H30 cm (W25 x D10 x H10 inches)

Evaluation: Despite a relatively small 60-cm-wide aquarium size, perspective is skillfully expressed by the layout composition and plant arrangement. In order to cover the short depth of the aquarium tank, the creator tried to create perspective by making a mound of substrate in the back and emphasizing the height difference between the front and back. This layout is created in a careful manner, even in the details of the four corners of the layout.

World Ranking #20

Piotr Dymowski


Title: The Virgin Stream

Dimensions: W120 x D60 x H50 cm (W50 x D25 x H25 inches)

Evaluation: The creator used the driftwood in a unique way and succeeded to give a soft impression to the layout with the use of selected aquatic plants. Perspective is effectively expressed by the white sand in the center. But the condition of foreground plants was a minus for this layout.

World Ranking #21

Wei Cheong Chung


Title: Titiwangsa

Dimensions: W150 x D60 x H45 cm (W60 x D25 x H20 inches)

Evaluation: Despite its title, a mountain range, the impression depicting the nature in details came as the first impression. The use of white sand extending from the foreground to the back is a standard layout technique, but the forefront line of sand should have been neatly leveled. An uneven front line gives a crude impression to the whole layout.

World Ranking #22

Katsuki Tanaka


Title: After the Rain in Mountain

Dimensions: W120 x D45 x H45 cm (W50 x D20 x H20 inches)

Evaluation: The composition and coloring of the layout create a picturesque impression. Beautiful red platy fish look like falling petals or colored maple leaves, but some people may not like such a stage effect. The composition of layout, emphasizing the perspective, is excellent.

World Ranking #23

Xue Hai


Title: Untitled

Dimensions: W242 x D90 x H100 cm (W95 x D35 x H40 inches)

Evaluation: The natural look of this layout is created with an impressive use of driftwood and ferns. The composition of the whole layout is good, but the left side of the layout looks incomplete. The layout would look much better by covering the back corner of the aquarium tank with more plants.

World Ranking #24

Piotr Beczynski


Title: The Late October

Dimensions: W90 x D45 x H45 cm (W35 x D20 x H20 inches)

Evaluation: In this layout, perspective is expressed by arranging twiggy driftwood in an arch style and having an open space in the center. Although some cosmetic sand is used, most of it is covered by aquatic plants and seems to be left unfinished. Despite the good condition of the aquatic plants, the condition of the white sand is a big drawback of this layout.

World Ranking #25

Cheng Jingqiu


Title: Glade

Dimensions: W120 x D60 x H50 cm (W50 x D25 x H25 inches)

Evaluation: The trees are created by driftwood and mosses. The intention of the creator is clearly conveyed with the image, but all the trees seem identical and they look like an artificially created tree-lined road. It is also regrettable that there is no difference in the sizes of the trees and perspective is not well expressed.

World Ranking #26

Haruji Takee


Title: Ryuoh Valley

Dimensions: W180 x D60 x H60 cm (W70 x D25 x H25 inches)

Evaluation: This iwagumi is one of a few standard Nature-Aquarium-style layouts among top prize winners. The layout may lack originality, but all the layout elements are well organized in its orthodox composition. The biggest drawback is the growth condition of aquatic plants.

World Ranking #27

Quan Nguyen Minh


Title: Green Paradise

Dimensions: W120 x D50 x H45 cm (W50 x D25 x H20 inches)

Evaluation: This layout reminds us of a scene in an unrealistic sci-fi movie. But the idea of floating rock was also seen in last year’s contest, and it is nothing new. Focusing on fundamentals of layout should be the priority rather than putting effort into the creation of an eccentric-style layout.

For a complete list of all the winners, please visit the official International Aquatic Plants Layout Contest website.

Posted January 24th, 2013.

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January 2013 Calendar

Tropical Fish Hobbyist’s January 2013 Desktop Calendar is now available!


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Visit the Web Extras section of for additional downloads, videos, and much more!

Posted January 1st, 2013.

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The Quick Guide to the Best Community Tetras

Diamond tetra. Photograph by Andrzej Zabawski.

By Lea Maddocks

In the January 2012 issue, I wrote about some of the best tetras available for beginners in the hobby.  The wide variety of shapes, colors, and behaviors of tetra species now available will leave most aquarists spoiled for choice when perusing their local fish store for new stock, and choosing can be a tough (but fun) ordeal. Tetras are also one of the first groups of fish new hobbyists begin with, as they are commonly available, small, colorful, and (generally) peaceful. Often, both new and long-term hobbyists will choose a tetra species or two to add activity and color to a community aquarium.

If you’re looking to purchase an one of the easier tetras, here is my quick guide to their basic needs and behaviors. For more information on any of these species, please check out my article.

Diamond Tetra

Size: 6 cm (2.4 inches)

pH: 5.5 to 7.0 for the best color, though tank bred specimens are very adaptable and can also tolerate more alkaline water, up to a pH of 7.5

Hardness: 5 to 12 dGH

Temperature: 24° to 28°C (75° to 82°F)

Tank Size: 75 liters (20 gallons) minimum, and at least 2 feet long. Ideally a 130-liter (35-gallon) or bigger tank is for better schooling behaviors and keeping a larger shoal. A 3 to 4 foot tank would be ideal

Tank Schooling Region: Middle to bottom, but generally all over

Notes: Prefers planted tanks with plenty of natural cover, this will bring out the best behaviours and coloration. Very peaceful. More in the school the better for effect and natural behaviours, minimum 6 per shoal, though 10+ is preferred.

Black Skirt Tetra

Size: 6 cm (2.4 inches)

pH: 6.0 to 7.0, though tank-bred specimens are very adaptable and will likely tolerate a range of pH from 6.0 to 8.0

Hardness: 5 to 20 dGH

Temperature: 20° to 28°C  (68° to 82°F)

Tank Size: 75 liters (20 gallons) minimum, and at least 2 feet long. Ideally a 130-liter (35-gallon) or bigger tank is for better schooling behaviors and keeping a larger shoal

Tank Schooling Region: Middle to bottom, but generally all over

Notes: Very forgiving of most water conditions and tank setups providing water is clean and the tank is cycled. Will be peaceful and co-habit well with most general community fish. The more that are in the school the better for effect and seeing their natural behaviours, with a minimum of six per shoal.

Buenos Aires Tetra 

Buenos Aires tetra. Photograph by Andrzej Zabawski.

Size: 7cm (3 inches)

pH: 6.0 to 8.0, the common tank bred specimens are very adaptable, they are reported to be happy between 5.5 to 8.5, one of the biggest ranges for a tetra

Hardness: 2 to 20 dGH

Temperature: 18° to 28°C (64° to 82°F)

Tank Size: 130 liter (35 gallon) minimum, at least 90 cm (3 feet) long to provide adequate territories and swimming space for this active fish. The bigger and longer the tank, the better. Would be a great choice for a standard 4 foot long, 200 liter (55-gallon) tank

Tank Schooling Region: Middle to bottom

Notes: A very hardy fish, likely to adapt to most tropical fresh water chemistries and temperatures. It is an active species which requires a good deal of open swimming space along with some cover to retreat into. Peaceful despite its active nature, though best kept with tankmates of a similar size and disposition, and bottom dwellers. Makes a great dither fish. Keep in shoals above eight to ten or more individuals to keep any pecking order activity among themselves.

X-Ray Tetra

Size: 4.5cm (1.8 inches)

pH: 6.0 to 8.0

Hardness: 2 to 30 dGH

Temperature: 24° to 28°C (76° to 82°F)

Tank Size: 40 liter (10 gallon) minimum. Ideally a 55-liter (15-gallon) tank or bigger will be better for schooling behaviors and keeping larger shoal

Tank Schooling Region: Middle to bottom

Notes: Given the annual flood cycles of its native waters, it is a very adaptable species that will fare well in just about any municipal water chemistry provided it’s kept clean and at the appropriate temperature. A very peaceful fish, it is best kept with other small and non-aggressive species. More in the school the better for effect and natural behaviors, minimum six per shoal with ten or more preferred as they will be confident in larger numbers.

Bloodfin Tetra

Bloodfin tetra. Photograph by Andrzej Zabawski.

Size: 5.5cm (2 inches)

pH: 6.0 to 8.0

Hardness: 5 to 20 dGH

Temperature: 18° to 28°C (64° to 82°F)

Tank Size: 75 liters (20 gallons) minimum, and at least 2 feet long. Ideally a 130-liter (35-gallon) or bigger tank is for this active swimmer

Tank Schooling Region: Top to middle

Notes: Very forgiving of most water conditions, providing water is clean and the tank is cycled. Will be peaceful and co-habit well with most general community fish. Excellent planted tank choice. More in the school the better for effect and natural behaviors, minimum six per shoal though eight to ten are better to prevent skittishness and reduce any minor intra-specific nipping.

Hockey Stick Tetra

Size: 6 cm (2.4 inches)

pH: 6.0 to 8.0, though tank bred specimens are very adaptable and will likely tolerate a range of pH from 5.5 to 7.5

Hardness: 5 to 20 dGH

Temperature: 22° to 28°C (72° to 82°F)

Tank size: 70 liters (20 gallons) minimum, at least 2 feet long. Ideally a 3foot long, or 130-liter (35-gallon) or bigger for keeping larger shoal and territorial behaviors in check

Tank schooling region: Top to middle.

Silvertip Tetra

Size: 5 cm (2 inches)

pH: 5.5 to 8.0

Hardness: 5 to 20 dGH

Temperature: 23° to 28°C (74° to 82°F)

Tank Size: 70 liters (20 gallons) minimum, at least 2 feet long. Ideally a 3 foot long, or 130-liter (35-gallon) or bigger for better schooling behaviors and keeping larger shoal

Tank Schooling Region: Top to middle, but generally all over

Flame Tetra

Size: 4 cm (1.6in)

pH: 5.5 to 7.8

Hardness: 2 to 20 dGH

Temperature: 22° to 28°C (72° to 82°F)

Tank size: 55-liter (15-gallon) minimum. Ideally 75 liters (20 gallons) or bigger for better schooling behaviors and keeping larger shoal

Tank Schooling Region: Middle, but generally all over

Lemon Tetra

Size: 4 cm (1.6in)

pH: 6.0 to 7.5

Hardness: 5 tp 20 dGH

Temperature: 22° to 28°C (72° to 82°F)

Tank size: 55-liter (15-gallon) minimum, or 2 feet long at least. Ideally 75 liters (20 gallons) or bigger for better schooling behaviors and keeping larger shoal

Tank schooling region: Top to middle

Posted December 21st, 2012.

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TFH Classic: New Discoveries in Peru


Photograph by Oliver Lucanus.

By Oliver Lucanus

From the January 2003 issue

Dwarf cichlids of the genus Apistogramma are among the most widespread cichlids in the Amazon basin. The genus is perhaps one of the most quickly expanding of all cichlid genera. Every year new species are scientifically described and further new varieties and new species are found. Apistogramma are now often split around groups, species flocks that have many common features within the group.

The A. nijsseni group is described to have the following species that all resemble the basic color patterns and body shape of A. nijsseni. While these groups are just a loosely arranged set of characters to describe similar species, they are often helpful in setting up the aquarium and water parameters for similar species.

A. nijsseni            Kullander 1979

A. panduro         Römer 1997

A. payaminonis                Staeck 1991

A. atahualpa     Römer 1997

A. norberti          Staeck 1991

A. sp. “Lyretail I”

A. sp. “Lyretail II”

A. sp. “Mouthbrooder”

With two new species to be added by this article:

A. sp. “red crescent/Inka,” the high fin nijsseni

A. sp. “black triangle,” the high fin panduro

All the species in this group have a round and high body shape. Females have a color pattern of spots or horizontal stripes. All of them live in blackwater habitats that run through the rainforests of Peru. Often the streams that these fish are found in are no wider than one meter and no deeper than 15 centimeters (6 inches). The substrate is often covered by leaf litter and has some terrestrial plants around its margins. Other fish common in all of these habitats are some small tetras, pencilfish (Nannostomus), Corydoras, and Crenuchus spilurus. There are few predators in this shallow water except for some knifefish and the wolf tetra (Hoplias sp.) that are present in nearly every habitat in the Amazon. Often these habitats are deep in the forest and far away from the main streams of the rivers and their flood zones that can extend for kilometers into the forest. Because of their distance from the main rivers and their ever-changing habitats these small streams are isolated and change little over the course of the year, which may well be the reason these fish could develop into such varied forms found in only tiny isolated areas. Of course this also makes the fish difficult to collect. Many of these fish have been discovered by aquarists searching small streams that cross roads and logging paths. In the absence of such access it may take hours of trekking through the jungle to find fish like these. This leads us to conclude that there are dozens more species to be found in the countless habitats of this nature found deep in the forest.

The two new Apistogramma are no exception. Their habitats are found nearly a day’s journey apart, but both fish unmistakably belong in the group of A. nijsseni –like fish. Apistogramma sp. “red crescent” was found by the German biologist Rainer Schulte. He has been living in Peru for many years to study poison arrow frogs and his search for frogs has taken him to many places in the Peruvian jungle. With his help, a Japanese group first managed to catch and export this spectacular fish last year. They named the fish A. sp. “Inka.” My expedition later that year yielded more Apistogramma of this new species as well as another Apistogramma species and a new Corydoras found in the same habitat. The habitat itself is typical for any fish from this group. The stream crosses a small logging road in several places and the fish are caught in water often less than 10 centimeters (4 inches) deep. In places where fallen trees have caused deeper pools to form, Corydoras and other Apistogramma species are found. This apisto is no less attractive and more similar to A. regani.

The water parameters in this habitat are: temperature 26°C (78°F), clarity 990 cm, pH 5.4, Fe (iron) 0.50 mg/l, GH 0, conductivity 15 µS, color blackwater, substrate white sand covered with leaf litter. The new Apistogramma is nothing short of spectacular. It has many features in common with A. nijsseni. The red margin around the tail, bright yellow ventral fins, and blue sides are common features of nijsseni. The most outstanding difference in the male is the spectacular dorsal fin that can be taller than the body of the fish, with all of the hard rays of the dorsal extended. Another very different feature to note is the more metallic blue flanks with several bars, not two spots like the typical form of nijsseni. The difference is even more extreme in the females: here the easily recognizable pattern of two spots (a large one on the flank and a smaller spot on the base of the tail) seen in A. nijsseni females is replaced by several vertical bars and a blue shine on the body.

In the aquarium the new species is much similar to A. nijsseni but requires larger tanks. The males require territories of at least 20 gallons each. Breeding females are fierce mothers that can defend large spaces even against much larger fish.

A day’s journey north another new Apistogramma was found. This species has common features with A. panduro but also features the dorsal fin extensions! The new fish has the same black triangle on the base of the tail and some extended rays on the dorsal fin. The black vertical stripes and blue shine on the flanks are also displayed in the males. Females are more similar to those of the new “red crescent/Inka” fish than those of A. panduro. Yet they feature only short vertical bars and a small round spot on their flanks. This variety is not nearly as aggressive as the other hifin Apistogramma and may be kept and bred in tanks as small as 15 gallons.

The new additions to this popular group of fish will bring them back to the most sought-after Apistogramma among hobbyists. With much attention paid to the slender Apistogramma species of the Rio Negro (A. diplotaenia, elizabethae, and mendezi) there has been little attention paid to new dwarf cichlids from Peru of late. Surely these stunning new fish will make them popular once again.

Posted December 6th, 2012.

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December 2012 Calendar

Tropical Fish Hobbyist’s December 2012 Desktop Calendar is now available!


Click on the size below that best matches your desktop.





Visit the Web Extras section of for additional downloads, videos, and much more!

Posted December 1st, 2012.

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TFH Classic: Salt and Other Sailfin Secrets

Sailfin molly. Photograph by Mark Smith.

By Robert Bock

From TFH December 2002

There are many controversies surrounding mollies. In this article, the past president of the North American Native Fishes Association reports his investigations and findings.


Want to start an argument among molly enthusiasts? Just bring up the subject of salt. One camp will say that you don’t need salt in the water to raise big, beautiful, sailfin mollies. Salt just allows lazy aquarists to compensate for dirty water, they say. It simply kills off the opportunistic bacteria and other parasites that victimize fish whose immune systems are stressed by the high nitrogen levels found in poorly maintained tanks. Keep fish densities low, do regular water changes, and you’ll have no problems raising big, beautiful sailfins that will be the envy of your fish club.

Not so, says the salt camp. Everyone knows that the biggest, most beautiful sailfin mollies come from saltwater habitats. Raising sailfins in fresh water produces, at best, small, stunted offspring that bear only faint resemblance to their wild forebears.

Who’s right? After keeping these beautiful fish for a few years, and conducting a little at-home research, I’ve come to the conclusion that they both are. For starters, sailfin mollies consist of three species, two of which are the most important for aquarists. Poecilia latipinna is found from South Carolina through Florida, along the Gulf Coast, and into Mexico. In the more southerly part of its range, P. latipinna is replaced by P. velifera, found along the coastal waters of the Yucatan Peninsula in Mexico.

These species resemble each other greatly, the major difference being that P. velifera usually has a larger body size, and the males have a larger dorsal fin than do males of P. latipinna. Male P. velifera have from 16 to 19 dorsal rays; male P. latipinna have only 12 to 14 rays. Both species inhabit brackish and freshwater habitats along the coast.

Commercially raised sailfin mollies come in an assortment of colors: black, white, mottled, yellow, and orange. In recent years, my favorite variation, the wild type “blue” sailfin molly, has started showing up in aquarium stores. The genetic pedigrees of these store-bought mollies vary greatly. They may be descended from P. latipinna or P. velifera, or hybrids of the two species, or from a hybrid of one or both species and some other related poeciliid species. Because of their mixed parentage, some of these mollies may not produce offspring capable of surviving on their own.

The Quest

I began my quest to raise the biggest, best sailfin mollies I could about four years ago. My friend, B. G. Granier, sent me a batch of wild-caught sailfin mollies, P. latipinna, from near New Orleans, Louisiana.  They were among the most beautiful creatures ever to grace my fishroom. There were about 10 males in the group, all of them shimmering azure and silver, each trimmed with orange on the face, dorsal, and tail fins.

Some people believe salt is needed to raise big, beautiful sailfin mollies, while others do not. Photograph from TFH Archives.

One by one, I watched them slip away. It began with a slight wobble. Their condition grew worse, until they could barely hold steady in the water. Eventually, they developed a downward curving spine.

At first I thought it was a contagious disease, brought in from the wild. I treated them with a variety of medicinal products. Nothing worked. One after another, they began to die. I wondered if it would be best to swear off this beautiful species for good before I killed any more. B. B. had warned me that they might need a little salt in their water to do well. But what I’d read said that salt was unnecessary, so I hadn’t added any.

The remaining male lingered in a quarantine tank. I pondered his curved spine and how much he reminded me of an older woman with osteoporosis. Perhaps he didn’t have a contagious disease. I remembered how some women develop osteoporosis later in life when they lack calcium in their diets during their reproductive years. Maybe this fish had a nutritional deficiency resulting from a lack of calcium.


I didn’t have anything left to lose. If I didn’t try something soon, the fish would probably be dead in a few days. So I dumped a tablespoon of garden limestone into the water. Limestone, I reasoned, is largely calcium carbonate and might provide a nutritional boost to help the fish hang on.

Soon after, the wobbling stopped. Although his spine never straightened out, this male lived on for many more months. Limestone, I soon learned, forms clumps and really doesn’t dissolve very well in water. Eventually, I began using another source of calcium carbonate—the Rift Lake salt favored by cichlid keepers. Within a couple of years I had four sailfin breeding tanks and an Everglades biotope tank crowded with sailfin mollies. Wild sailfin females are a drab gray, resembling large female guppies. To add a little color to the tank, I began keeping orange and mottled sailfins I bought at the aquarium store.

According to the books and articles I’d read, sailfin mollies inhabit salt water, brackish water, and fresh water. In an aquarium they would do well under any of these conditions. But what I’d read hadn’t explained why the fish seemed to need a calcium-rich environment.

Salt or Calcium?

A short time later, I happened upon the work of Joel Trexler, an ecologist at Florida International University in Miami. Dr. Trexler studies the effects of environmental influences on evolution. One of his major research interests is on how environment influences the development of sailfin mollies. I told Dr. Trexler about how adding garden limestone to the tank saved my sailfins from certain doom. He explained that sailfins are more suited to life in salt water than in fresh. Specifically the gill structures of sailfin mollies have osmoregulatory systems more like those of marine species. Osmoregulation refers to a fish’s ability to maintain the balance between the sodium and other minerals inside its body and the sodium and mineral concentration of the water it lives in.

Many fishes, including sailfin mollies, can use calcium in place of sodium for maintaining their osmotic balance, he said. For sailfins, water with high carbonate hardness also explains the distribution of sailfin mollies, at least throughout the East Coast. At the top of their range, in South Carolina, P. latipinna are confined to the salt and brackish waters along the coast. In southern Florida, their range extends across the peninsula. Much of south Florida sits atop ancient coral beds, and so its water have fairly high carbonate hardness. Similarly, P. velifera are either found in saltwater habitats or in limestone springs, and the geology of the Yucatan has much in common with southern Florida.

Calcium carbonate works the same way as salt when added to the molly aquarium. Photograph by Mark Smith.

One caveat is worth inserting here. A few populations of sailfin mollies might be genetically adapted to survive without salt or calcium carbonate. Virtually all the mollies I’ve kept die if they aren’t kept in very hard water, with a pH of at least 7.8. However, Bill Allen, of the American Livebearer Association, has told me of a drainage ditch full of sailfin mollies in Shreveport, Louisiana, about 200 miles from the Gulf Coast. The mollies there are apparently thriving in a pH of about 7.0, with total dissolved solids of less than 100 parts per million.

To complicate the great salt debate even further, many aquarium strains of sailfin mollies may have resulted from crosses with other freshwater species. In an email, Trexler told me that long-time commercial fish breeder Ross Socolof had told him that the aquarium black molly strains were developed from crosses between P. velifera and the  freshwater species, P. sphenops. For this reason, P. sphenops genes may have provided some strains of commercially available sailfins with a greater tolerance to fresh water than their wild-caught cousins have. However, with one or two exceptions, the store-bought sailfins that I’ve kept have done better in sea water than they have in fresh.

Salt and Calcium?

Although sailfins need calcium carbonate to maintain their osmoregulatory system, I have a theory that—because of the hunched backs that my fish developed—they may also have a higher nutritional need for calcium than other fish do. The males’ large dorsal fins contain numerous elongated rays, which may require extra calcium to develop. Dietary calcium may be available to them in algae and microscopic crustaceans they eat, having been absorbed by the latter from the water they live in.

I should point out, though, that Trexler questions the need for extra calcium in the sailfins’ diet. Armored catfish, he said, come from a soft water environment with little calcium and don’t seem to need any extra calcium to develop their armored plating. Since no scientific studies have been done on sailfins and dietary calcium, however, there isn’t any evidence to prove either of us right or wrong.

The Data

The varied conditions that wild sailfin mollies live under provide a natural laboratory that Trexler’s group employs to study the effects of environment on an organism.

One of his group’s experiments, in particular, is relevant to aquarists. He and his coworkers collected sailfins from four different locations throughout Florida. They raised the offspring of these fish under a combination of different conditions to see how those conditions might affect the fish’s development.

The scientists raised the mollies individually in 5-gallon aquaria in water with three different concentrations marine salt, 2 ppt (parts per thousand), 12 ppt, or 20 ppt. The fish were kept at a temperature of either 74° or 84.2°F and were fed either the maximum amount of food the fastest-growing individuals could eat in one day, or half that amount. The scientists reared groups of fish in each of the 48 different combinations possible.

Before beginning the study, Trexler and his colleagues did some informal tests to determine if the fish actually needed salt. The researches learned that the mollies grew more slowly and were more likely to die from fungal infections in water that had no salt. In water with 2 ppt salt, virtually no fish died.

Surprisingly, the amount of food the fish were given—a good quality flake—didn’t vary enough to have an effect on their final size. The greatest size at maturity, however, was reached by fish kept at 84.2° in water with a salinity of 2 ppt. Although their gill structure suggests that sailfin mollies do benefit from some salt in the water, that amount doesn’t seem to be that high. It’s worth noting here, also, that Trexler’s study tested only three salt concentrations, so it’s impossible to generalize from them which salinity level mollies favor most. It does seem reasonable to conclude, however, that the ideal salt concentration for most sailfin mollies lies somewhere between 2 ppt and 12 ppt.

The lack of an influence for high salinity on body size, however, is puzzling, particularly in light of other, seemingly contradictory findings. In field studies, scientists have observed that the largest sailfins were found at higher salinities in their wild habitats. Similarly, in another experiment, Trexler and his colleagues found that, in outdoor cages, mollies grew larger in sea water than they did in fresh water. The researchers theorized that some unknown condition in the wild might favor the development of larger size at higher salinities. I’ve observed much the same thing in my own tanks. The sailfin mollies I raise in artificial sea water also seem to be larger than those I raise in fresh water.


I suspect that the unknown condition may be diet. According to Trexler, sailfin mollies are largely herbivores. Like mammalian herbivores, they have long, winding digestive tracts suitable for digesting plant matter. He and his coworkers have analyzed the stomach contents of wild sailfins and found them to contain mostly algae. So, too, mollies kept in aquariums spend nearly all their waking moments grazing on algae.

My hunch is that the faster growth I’ve seen in my saltwater aquariums and that Trexler and his group saw in their saltwater cages could be from marine microalgae. Marine microalgae may be more nutritious for sailfins than freshwater microalgae is. Alternatively, marine microalgae may simply be more palatable than freshwater microalgae. Mollies that I’ve kept in saltwater tubs in summer and in brightly lit saltwater aquariums in house always look well fed, even when I hadn’t fed them for a couple of weeks. In contrast, freshwater mollies I’ve kept under the same conditions in freshwater always look underfed. The freshwater microalgae seems to be harder than the saltwater microalgae, and so I think the fish simply can’t consume enough of it to meet their needs.

My hunch is that if you can feed mollies a sufficient amount of food in either hard fresh water or in 2 ppt sea water, they will grow as large as mollies kept in brightly lit seawater environments.

To test this, I’ve divided baby molly siblings from the same wild-caught mother into two groups. I’m rearing one in sea water and another in hard fresh water. Except for the salinity, I’m keeping both groups under nearly identical conditions. To make sure they get enough to eat, I allow both groups to graze nearly all day on cubes of high density food I make myself.

I feed homemade cubes because I don’t think it’s possible to raise large mollies on a diet of dry flake food, unless, perhaps, you can find the time to feed them a dozen or so times a day. Dry foods are less dense than pellets and frozen cubes, so feeding flakes two or three times a day, as most aquarists are able to do, simply won’t supply them with the comparable amount of nutrition they could get by grazing on marine microalgae all day.

To make my pellets, I begin by soaking high quality cichlid pellets until they’re water logged. As most aquarists know, fish can die if they eat too much dry food; the food takes on water inside the fish’s digestive tract, and the fish’s digestive organs burst. In contrast, fish can eat as much water-logged food as they like. I mix the pellets with an equal amount of unflavored gelatin other ingredients and turn on the blender until I have a dense slurry. I pour the slurry into empty plastic frozen fish food containers to form individual portion sizes, then freeze portions until I’m ready to use them.

Currently I’m still experimenting with the food mixture, and I’ll often add frozen brine shrimp, cooked peas, soaked flake, and marine macroalgae.

It’s been about a month since I’ve started keeping two groups of fish under these conditions. So far, the freshwater sailfins seem to be keeping pace with their saltwater siblings.

One promising idea that I hope to get around to eventually is to provide mollies kept in fresh water with algae grown in sea water. One way to do this would be by rotating algae-covered rocks from a seawater tank through the freshwater tank.

Growth Dimorphism

Another important lesson to learn from Trexler’s study of environmental conditions is how female body size is influenced more by environment that is male body size.

Although their environment clearly influenced the size of both sexes, female mollies reach their greatest size largely because of environmental conditions favorable to growth, whereas males reached their largest size because of the genes they had inherited. This finding confirms earlier studies, which suggest that male body size depends largely on a number of different genes. Male sailfins mature at various stages of development. When they reach sexual maturity, they stop growing.

The implication for hobbyists, though, is clear: If you want to raise a strain of large, colorful sailfins with big sails, it’s best to start with large male breeders. Keeping small males in the hopes that they will reach a large size, then, is fruitless. Instead, small males should be ruthlessly culled from the breeding tank, as their sons will also be small.

Personally, I select for female size and color. Although I prefer the coloration of wild-caught males to that of their store-bought cousins, female wild-type sailfins are rather drab. Right now, I’m trying to introduce some color into the females, both with store-bought orange varieties and with wild-type females having some faint orange coloration. If I come across an outstanding wild-type male, I’ll add him to my breeding stock, both to add new male genes and to prevent inbreeding. I don’t pay attention to whether my breeders are P. latipinna or P. velifera. Since both species interbreed freely, I’m not interested in maintaining a pure strain, just in producing an outstanding strain of blue males for the aquarium.


So, what about the Great Salt Debate? Mollies probably have the best chance for thriving if they are kept in water that is at least 2 ppt salt or has a pH of 7.8 or higher and is hard and alkaline. Although mollies will greedily take meaty foods such as insect larvae and brine shrimp, they are herbivores. No matter what  you feed them, it’s probably best to keep them with an abundance of algae to graze on.

Because they graze continually, sailfins produce large amounts of ammonia-containing wastes. For this reason, tank densities should be kept low. Low tank densities not only keep down levels of ammonia and other wastes, but also prevent stressful competition between males. The high pH that sailfins favor increases the ammonia’s toxicity, so would-be sailfin keepers need to take extra pains to keep ammonia levels down through frequent water changes, good filtration, and perhaps with the assistance of ammonia-absorbing, fast-growing plants.

For freshwater sailfin tanks, I grow Italian vals (Vallisneria spiralis), in salt water, the marine macroalgae Caulerpa taxifolia. Bright lighting will not only stimulate plant growth, but also that of macroalgae the mollies need to graze on. Although they’ve been in the hobby for many years, sailfin mollies are not a beginner’s fish. They do require some extra work, and some extra thought. But the beautiful colors of both store-bought and wild-caught fish, plus the magnificent sail stretching display of courting males, merit the attention of serious aquarists.


I’d like to thank Dr. Joel Trexler for his careful review of this manuscript. Articles on wild sailfin mollies are available on the website of the North American Native Fishes Association In addition, the American Livebearer Association has an excellent compilation of past articles on mollies


Posted November 21st, 2012.

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Best Plants for Beginners

By Lea Maddocks

As Lea Maddocks explains in the second part of her article in the December 2012 issue,  Setting Up a Successful Low-Tech Planted Tank Like a Pro, Part 2: Aquascaping and Maintaining Your Planted Tank, choosing aquatic plants that fit your skill level and fit the look that you want can be challenging. However, some plants have a reliable track record of doing well in low-tech setups.

Let’s start with the best epiphytic plants. These should not be planted in the substrate, instead they can be tied to rocks or stones and allowed to grow with their roots exposed.

Java fern and Java moss are both very hardy plants. Photograph by Gary Lange.

Java fern varieties (Microsprum pteropus) including regular, crested (aka ‘windelov’), and narrow leaf

Anubias species

Congo fern – Bolbitus heudelotii

Mosses, including Java moss

Next come floating plants. Similar to epiphytic plants, these should not be buried in the substrate. Instead they should be left floating freely in the aquarium. They are great for providing shade to skittish fish.

Duckweed is an easily grown floating plant, but be warned that it can easily reach plague proportions. Photograph by Albert Connelly, Jr.

Hornwort (Ceratophyllum demersum)

Lacefern/watersprite (Ceratopteris thalictroides)

Duckweed (Lemna minor)

Mosquito fern (Azolla caroliniana)

Brazillian pennywort (Hydrocotyle leucocephala)

Water lettuce

Some stem plants are appropriate for beginners. These must be planted in the substrate.

Green hygro (Hygrophila polysperma) is a relatively easy-to-grow stem plant. Photograph by MP. & C. Piednoir.

Some ludwigia, including the red Ludwigia repens

Elodea/Egeria – Egeria densa

Green hygro (Hygrophila polysperma)

Water wisteria (Hygrophila difformis)

Lacefern/watersprite (Ceratopteris thalictroides, note this can be planted as a stem plant or left floating)

Brazillian penny wort (Hydrocotyle leucocephala)

Bacopa – Bacopa australis, B. monnieri, Bacopa caroliniana


Myriophyllum mattogrossense

Amazon swords, the ozelot variety has red flecks and can be great for color

Rotala rotundifolia

Cryptocoryne species, especially browns like C. Wendtii, C. Lutens

Pearlweed (Hemiantus glomeraturs), which was formerly confused with H. micranthemoides

Saggitaria and dwarf sgaggitarita

Pygmy chain sword (Helanthium tenellus)

Posted November 16th, 2012.

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November 2012 Calendar

Tropical Fish Hobbyist’s November 2012 Desktop Calendar is now available!


Click on the size below that best matches your desktop.





Visit the Web Extras section of for additional downloads, videos, and much more!

Posted November 1st, 2012.

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