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Captive breeding could transform the saltwater aquarium trade and save coral reefs, biologists say


Dr. Joan Holt is the associate director of the Fisheries and Mariculture Lab at the University of Texas at Austin Marine Science Institute in Port Aransas. She’s done pioneering work in the field of marine aquaculture, and has helped launch a movement to change the way that fish are raised and sold for saltwater fish tanks.

Credit: Scott Holt

Marine biologists at The University of Texas at Austin Marine Science Institute are developing means to efficiently breed saltwater aquarium fish, seahorses, plankton and invertebrates in captivity in order to preserve the biologically rich ecosystems of the world’s coral reefs.

These scientists believe their efforts, and those of colleagues around the world, could help shift much of the $1 billion marine ornamental industry toward entrepreneurs who are working sustainably to raise fish for the aquarium trade.

“It’s the kind of thing that could transform the industry in the way that the idea of ‘organic’ has changed the way people grow and buy fruits and vegetables,” says Joan Holt, professor and associate chair of marine science at The University of Texas at Austin. “We want enthusiasts to be able to stock their saltwater tanks with sustainably-raised, coral-safe species.”

Holt is a co-author of a recent article, “Advances in Breeding and Rearing Marine Ornamentals,” published in the Journal of the World Aquaculture Society in April.

The paper is a complement to Holt’s broad-ranging work over the past 10 years to promote captive breeding of ornamentals. She’s been a pioneer in developing food sources and tank designs that enable fragile larvae to survive to adulthood.

Holt has also been a vocal critic of the extraordinarily wasteful methods currently used to bring sea creatures from the oceans to the tanks.

“One popular method is to use a cyanide solution,” says Holt. “It’s squirted into the holes and crevices of the reef and it anesthetizes the fish. They float to the surface. Then the collectors can just scoop them up, and the ones that wake up are shipped out.”

This method, says Holt, has a number of unfortunate effects. It bleaches the coral. It kills or harms other species that make the coral their home, particularly those that can’t swim away from the cyanide. It can deplete or distort the native populations of the species. And it contributes to 80 percent of traded animals dying before ever reaching a tank.

Unlike the freshwater ornamental market, which relies mostly on fish raised in captivity, the saltwater ornamental market is 99.9 percent wild caught. Holt says this is largely because there’s less accumulated knowledge on breeding saltwater fish in captivity. Saltwater species also tend to spawn smaller, less robust larvae, which are harder to rear to maturity, and to rely on various foods, such as plankton, that are not readily available in mass quantities for breeders.

Yet all these difficulties, says Holt, are surmountable.

She and her colleagues in Port Aransas, where the Marine Science Institute is located, have successfully bred in captivity seven species of fish, seahorses and shrimp they’ve caught from the Gulf of Mexico and the Caribbean, including species that other biologists had tried but failed to rear before. Others have successfully bred popular species like clownfish, gobies, dottybacks, and dragonets, as well as coral, clams, invertebrates, and algae.

Several big aquariums, including SeaWorld, have committed to assisting in the breeding and egg collection effort, and to integrating into their exhibits information about how the aquarium trade impacts the coral reefs.

Holt and her colleagues envision, ultimately, is a “coral-safe” movement. The science, the economics and the social awareness could together result in a sea change in how saltwater aquariums are populated and how saltwater tank enthusiasts think of themselves and their passion.

As more tank-raised ornamentals percolate into the market, Holt believes people will see another advantage to buying sustainably. The fish will simply do better. They’ll live longer, be healthier and be easier to care for.

“Species that are bred in captivity should adapt much better to your tank than something that was just caught halfway across the world, in a different system,” says Holt. “Good retailers will want to sell these species, and consumers will benefit from buying them.”

Source: University of Texas at Austin

Posted June 2nd, 2015.

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Breeding Common Fish

By Mike Hellweg

As promised, I spent some time in a couple of local big box stores and a couple of local fish stores. In both big box stores the pickings were mighty slim for me— mostly big fish like cichlids. But there were a few nice small fish from which I selected some potential breeding stock.

The local fish stores were even better. I was able to go into one and find several pairs of tetras and barbs that were old enough for spawning. Even better, in one I was able to get them all on sale at a huge discount! And in the other, I was able to trade a bunch of young fish from the contest for several pairs and a couple of breeding groups that were almost ready to go. This illustrates one of the great reasons to support your local shop—I was able to trade in some of my breeders to one local shop and get a couple more species in exchange.

So in a couple of hours, with a couple of stops, spending only about $25, I re-homed a large number of fish and brought home enough fish to keep me busy for at least a couple of weeks in the contest.

Obviously, all of the fish, even those I get from friends, go into quarantine first. No sense introducing disease into an established tank.

Here are some of the fish I found:


Pseudocrenilabrus philander

Livebearers and Killies:

Wild-type green swordtails Xiphophorus hellerii

Coral red platies Xiphophorus sp. domestic platy

Sunset variatus Xiphophorus sp. domestic variatus


Corydoras narcissus (marked as skunk cories – Corydoras arcuatus)

Corydoras paleatus

Egg Scatterers:

Pearl danio Danio albolineatus – these were on sale for just 11 cents each!

Zebra danio Danio rerio – 11 cents each!

Blue danio Danio sp. – 11 cents each!

Fireline danio Devario sondhi

Black skirt tetra Gymnocorymbus ternetzi

Silvertip tetra Hasemania nana

Glowlight tetra Hemigrammus erythrozonus

Head and tail light tetra Hemigrammus ocellifer

Pretty tetra Hemigrammus pulcher

Ember tetra Hyphessobrycon amandae

Columbian redfin blue tetra Hyphessobrycon columbianus

Sickle fin tetra Hyphessobrycon robertsi

Serpae tetra Hyphessobrycon serpae

Neon tetra Paracheirodon innesi

Tiger barb Puntius anchisporus

Melon barb Puntius melanampyx

Black ruby barb Puntius nigrofasciatus

Gold barb Puntius semifasciolatus or Puntius “sachsi”

White cloud mountain minnow Tanichthys albonubes

Penguin tetras Thayeria obliqua


Honey gouramis Colisa chuna

Pearl gouramis Trichogaster leeri

Gold gouramis Trichogaster trichopterus

Marine Fish:

Tank Raised Bangaii Cardinals Pterapogon kauderni

And a group of spotted loaches – no idea what species they are but they are easily sexable, so I’ll keep my fingers crossed!

Since Ted mentions it, I’ll stress again how important quarantine is to success with aquarium fish. Several of the neon tetras and fireline danios came down with ich soon after arriving home. It is likely the cold weather somewhere in transit, either at the airport here before they made it to the shop, or in the delivery truck stressed them and made them susceptible. Fortunately, I followed my normal procedure and put the new fish in quarantine tanks. The ich only affected two of those tanks. I was able to treat it immediately since I was watching for it, and only lost a couple of fish. The rest came through with flying colors. Of course this sets any breeding attempts with those two species back several weeks as they will need time to recover. But I’ve got plenty of fish to work with for the next few weeks.

Posted June 2nd, 2015.

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Yarn is Easy

By Ted Judy

The store clerk says, “You buy a lot of green yarn.”

To which I reply, “I like the color green.”

“A whole 10 bundles worth of green?” she asks.

“Sometimes I buy dark blue.  But only when you are out of green.”

Miss Nosy presses, “You buy all the green.  I think you are the only person who buys it.  Why so much yarn?”

“Mops,” I replied with a look that suggested it is perfectly normal to buy 10 large packages of green acrylic yarn to make mops.

“You make your own mops?”


“There are better mops in housewares.  Thicker.  Made of cotton.  They hold water better.”

“But those are white.  And cotton rots.  And they’re way too big.”

“To0 big for what?”

“Mops.  And it is too hard to see eggs in a white mop.”

She stares at me for a moment, and turns away as she concludes, “Have a nice day, sir.”

Aquatic plants are the egg depositories, nurseries, and fry-food larders in most of the ecosystems from which most of our aquarium fish originate.  In some places the water is shallow and in a sunny place, permitting dense growths of plants all through the habitat.  Other places have deeper or fast flowing water that limits the vegetative cover to the shoreline.  And there are many places, such as deep under the canopies of forests, where there is not enough light to grow plants well.  And yet, even in these light-starved locations there will be enough plant growth to provide fish a place to spawn and the fry a place to start life.

Except in my fish room.  I am notoriously bad at growing aquatic plants.  I have a few forlorn clumps of java moss here, a bit of various water weed there and some ever-present duckweed on one or two tanks.  I try to grow plants.  I rarely return from an auction without a few bags of vegetation.  I will always buy guppy grass Najas sp., overpay for Java moss, and bid competitively for frog bit and water lettuce; but no matter how much I bring home I am in need of more within a couple months.  So I dutifully buy the plants and they dependably fall apart into lovely detritus (decaying plants that many fish love to eat).  Not a perfect system, but it seems to work for me.

Except that adult fish need plants to lay eggs in and their fry need a place to hide and forage for food.  Since I cannot count on having a dense growth of live plants to provide these places, I have learned that the next best thing is yarn.  Yarn mops are the staple for killifish and rainbowfish breeders, but yarn can be used by any fish that lays its eggs in plants.  The trick is in how the yarn is presented, and to get the presentation right it is important understand how the fish use plants.

Egg Placers

Some fish are very specific about where they lay their eggs.  They do not lay many at one time and will carefully choose where to put them.  Killifish and rainbowfish are good examples of these egg placers.  The eggs are adhesive, and they stick where they are laid.  Males will stake out territories in an area where the females are likely to want to lay their eggs.  This might be a particularly dense growth of plants in nature, but in my fish room it is a strategically placed mop of green yarn.  Egg placers can be picky.  Some species prefer to lay their eggs in the middle of the mop, and will work very hard to get themselves as deep into the yarn as possible.  Other species will barely enter the mop at all, and lay their eggs in plain view on the outside of the bundle of yarn.  Sometimes the place where a female lays her eggs is different between individuals.  I have a colony of pygmy rainbowfish Melanotaenia pygmaea, and some of the females choose the very top of the mop and others prefer the very bottom.

Egg placers like rainbow fish and killifish will readily use a yarn mop.

I was surprised to learn that some species of Corydoras catfish will deposit eggs in a yarn mop.  Cories are one of the most deliberate of all egg placers.  The female will carry a few eggs between her ventral fins, clean a site with her barbels and then meticulously place her very sticky eggs on that spot.  The first cory I worked with that used a mop was C. panda, which is a relatively easy cory catfish to breed and is readily available in the hobby.  Condition them with a lot of high quality food, including live foods such as black or white worms, and give them frequent water changes with cool, clean water of medium hardness and a neutral pH.  Leave a mop hanging from the surface to the bottom in the tank near the current of the filter.  The panda cories will also lay eggs on the sides of the tank, so when eggs appear on the glass there are probably also eggs in the mop.  I remove the entire mop with eggs to a hatching tank and add quite a bit of methylene blue to the water (2 to 3 drops per gallon), and I have found that there is a much greater hatch and survival rate than without the medication.

Egg Scatterers

Almost all of the characins and cyprinids (tetras, barbs, danios, etc.) like to scatter their eggs over plants.  Egg scatterers fall into one of two categories that I use to describe them.  The first are the true scatterers.  The males of these species chase the females all over the tank until the females give up trying to get away and just dump their eggs.  I do not know if egg release is a stress response or not, but I have had very gravid congo tetra Phenacogrammus interruptus females unload a lot of eggs while being chased around the tank with a net (which does not leave many eggs left for spawning later, so net carefully).  The pairs or spawning groups will dash about all over the tank dropping eggs and milt wherever they go.  The fish in the group that are not spawning will usually scurry around after the spawning fish eating the eggs just as fast as they are laid.  This is when the yarn is useful.  In nature the eggs would fall into dense thickets of plants, but in my tanks the eggs fall into yarn.  Lots of yarn.  When I use a 10-gallon tank for spawning an egg scattering species I will place a layer of tangled up yarn in the bottom that covers the entire surface area to a depth of 4 to 6 inches.  The fish will spawn over the yarn, into which the eggs fall and are therefore harder for the other fish to find.

Egg scatterers that need a large tank will spawn over a yarn egg trap is if it were grass.

The second group is the secretive egg scatterers.  These fish are a bit like the egg placers, but the eggs are not adhesive so they fall into the yarn rather than stick to it.  Most of these species are small and shy.  Some spawn every day and only lay a few eggs at a time.  A good example of this type of fish is the celestial pearl danio Danio margaritatus, which is also called the galaxy rasbora.  These shy little fish are easy to keep and breed in a very small tank.  I use a 2.5-gallon aquarium with a small sponge filter and a dense layer of yarn.  The fish are very shy and the yarn provides excellent cover for them.  I have found that a pair is best in a tank that small because the other fish will find and eat the eggs.  I leave the pair in the tank for a week and then remove the pair.  After a few days I carefully lift up the yarn and use a flashlight to look for fry.  The danios rarely disappoint.

Small scatterers, like these ember tetras, like to bury their eggs deep in dense plants… or yarn!

I also use yarn to build egg traps for larger tetras, barbs, or danios to spawn over in a larger tank.  The trap is basically a plastic box with a wide-mesh top into which 2 – 3 inch pieces of yarn are woven.  I place the box in the larger tank with the fish out in the open.  When the fish spawn they usually make scattering runs over and through the yarn sticking up from the trap.  The eggs filter through the mesh and end up safe and sound inside the plastic box.  This system is especially useful for species that take a while to settle into a spawning tank, so moving them from conditioning tank to spawning tank just upsets them.

Yarn can also be used over a false bottom that the eggs will fall through, protecting them from being eaten.

Traps are also good to use when the species is a very sporadic spawner.  I keep traps in all the tanks I have larger African tetras in.  Species like the yellowtail congo tetra Alestopetersius caudalis, the African red-eye tetra Arnoldichthys spilopterus, or the long-fin Alestes tetra Brycinus longipinnis.  It is hard for me to predict when these fish will spawn, but I dutifully check the trap every day and find eggs in there once or twice each month.


I also use yarn to provide a place for livebearing fish to release their fry.  Some livebearers are notorious for eating their fry almost as soon as they are free swimming.  Guppy traps are useful tools, but try using one for a 4-inch Ilyodon furcidens or other large and powerful Goodeid livebearers.  Even some of the larger female swordtails would challenge the average guppy trap.  I prefer to use a 2.5-gallon aquarium with a lot of yarn.  I use large mops that drape a along the bottom for this purpose.  The mops are thick and take up a lot of space in the water column, but leave enough room in the upper half of the tank for the female livebearer to swim freely.  The bottoms of the mops lie in a heap on the bottom.  When the fry are born they can drop into the yarn at the bottom to hide.

I move the females to a birthing tank when they are three to six days away from giving birth.  How do I know when that is?  I use a calendar.  The gestation periods for most livebearers are well-known, and a little research on the Internet is all that is usually needed to get that information.  Like all of my breeding fish, I like to condition females and males separately, and then put them together when they are fat and happy.  Most livebearers are very efficient when it comes to impregnation, so I mark the calendar on the day I put the males in with the females I want to breed.  I leave them together until the females are noticeably pregnant and then move them back to the conditioning tank; or I leave the females in with the male until the calendar tells me the fry could be born in a few days.  Once the female goes into the birthing tank I check for babies several times a day.  Once the fry are born I try not to leave the female in with them any longer than necessary.  I am also very careful to make sure that a female in the birthing tank is well fed.  I figure that a hungry female is more likely to eat her fry, but I have no evidence to support or refute that claim.  Seems like common sense to me.

The Ease of Yarn

Yarn does not die.  It will stay just as lush and vibrant regardless of the light, pH, temperature or hardness.  It comes in a rainbow of colors (though I prefer dark forest green).  And, best of all, a fish does not care if it has yarn or plants, so long as it has a place to lay eggs and hide its babies.  Yarn is easy.

Posted June 2nd, 2015.

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Sneaking Success

Neolamprologus pulcher. Photograph from TFH Archives.

By David E. Boruchowitz

Cichlids demonstrate extremely sophisticated reproductive strategies. One of the least common involves cooperative breeding in groups or colonies. Lake Tanganyikan Neolamprologus pulcher breed en masse, with the entire colony rising as one to fend off predators, and with non breeding individuals participating in the care and protection of the offspring.

Aquarists have long known about this behavior, which is more obvious in the wild, where hundreds of fish are involved, but which translates in captivity into breeding groups that avoid the typical predation on the fry by non parental adults in the same tank.

A new study reveals that about 10 percent of the fry produced in these colonies are sired by subordinate males, and that those males are more diligent in protecting the young.

This is reminiscent of the situation in several Xiphophorus swordtails, where smaller, inconspicuous males rely on sneaking rather than courtship to father a small percentage of fry. In both cases subordinate males father a small but significant number of offspring, though in the case of the swordtails it is a matter of genetic castes among the males, not just one of dominance.

Posted June 2nd, 2015.

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Spawning Pygmy Cories

By Jennifer Wilkinson


Pygmy cories appreciate a well planted tank with plenty of cover. Photograph by Mark Smith.

The pygmy cory (Corydoras pygmaeus) is found in South America, but was originally discovered in the Rio Madeira system. They seem to be readily available to aquarium hobbyists at certain times of the year.

This dwarf cory can reach about an inch in length. It is a grayish brown color on the top and a lighter gray on the bottom. The two colors are divided by a dark line that runs the length of the body to the caudal peduncle. The line ends with an almost round dot on the caudal peduncle, which is surrounded in a lighter color. The rest of the caudal peduncle and fins are a clear color. The females are slightly larger than the males and especially when ready to spawn. C. pygmaeus are part of the elegans group, along with C. elegans, C. hastatus, C. undulatus, C. latus, C. guapore, C. nanus, and C. gracilis.

Cory Behavior

Pygmy cories can be found on the bottom of the aquarium, like most other cory species. However they also like to swim in midwater, about 4 inches from the bottom. They also have the capability to hover in one spot. I have kept many species of Corydoras and have found that not too many do this. If the aquarium is set up properly so that the dwarf corys are comfortable, they will be seen dashing about all day long.

If there is any motion around their aquarium or if they feel threatened they will dash off into a hiding spot. If they can’t find a hiding spot, they will come to a standstill on the bottom of the aquarium and only begin to move again when they feel the danger has passed. All the Corydoras I have kept seem to be more comfortable in an aquarium that has lots of caves, rocks, flower pots, and live and plastic plants. They seem to be more comfortable if they are under something, so providing some kind of cover is necessary. They will also dash up to the top of the aquarium to get a gulp of air.

In the aquarium they prefer to be in large groups of the same species or with other species of Corydoras of about the same size, as they are very social little fish. I usually recommend that all Corydoras be purchased in groups of three or more because of this social behavior. If at all possible, I recommend at least six, and more is definitely better with these little fish, especially in a community aquarium. In the wild these fish are found in very large groups, hundreds or thousands are not unheard of.

Bringing Them Home

I had to special order my fish from one of the pet shops I was dealing with at the time. I ordered 20 C. hastatus. When I went to pick my order up, I questioned the owner about the fish he got in. When I examined the lot, I was sure that they were not C. hastatus but C. pygmaeus. It didn’t really matter to me which one they were, as I didn’t have either one. However, the store assured me they were C. hastatus.

They were very young, approximately seven weeks old, so it was very difficult to tell just what they were. The store owner threw in two extras just in case he counted wrong. So, on the way home from the store, I wondered just what kind of fish I had and just how many I had.

When I got home I placed my tiny cories in a 20-gallon aquarium by themselves. The parameters of this aquarium were a temperature of 78°F, the pH was 7.0, and the water was soft. This aquarium was filtered with an appropriately sized external power filter with a sponge on the intake tube so these little fish wouldn’t get pulled in. Water changes were done twice a week, with about 30 percent being changed each time.

The fish were raised and conditioned on sinking wafers, several different kinds of flakes, and baby brine shrimp. After four months a few eggs were found and I was surprised to find that there was also one half-grown baby. The eggs and the one baby were moved to a 5-gallon aquarium. Two days later, all of the eggs had fungused, so I decided to move the one tiny fry back in with the adults. Unfortunately two days later he was found belly up on the bottom—he probably couldn’t handle the stress of being moved so often.

Real Breeding Attempt

Shortly after, more eggs were found. This time, after doing lots of research, I was ready to try some different techniques. What works for one hobbyist may not work for the next, so I was prepared to have many flops before actually getting a viable spawn. This time I tried suspending a net in the main tank, with a gentle flow of air bubbles under it. Then I collected the eggs with my fingers and put them gently in the net. All the eggs fungused by the next morning.

The next batch of eggs were moved into a shallow glass pan with no air stone or filter. This time they hatched, but all was lost again three days later. I believe polluted water was the cause this time. These fry are really tiny, and certainly not near big enough to eat baby brine shrimp, so a liquid fry formula was fed. Obviously way too much of this, as the water became very cloudy and a water change wasn’t done fast enough. After this I gave up for a while, or I guess you could say I took a break.

I have used this shallow glass pan method several times now with other cories and Aspidoras spp. with great success. The difference being, as soon as the fry hatch and fall to the bottom, they are transferred to larger quarters (an aquarium) to be fed. More water means less pollution. Liquid fry foods are no longer used, instead artificial plankton rotifers are used until baby brine shrimp can be fed. Lots and lots of water changes are a must. If only I would have known at the time.

Success at Last

I finally had success with these pretty little corys when I moved them into another 10-gallon aquarium down in the fishroom. They were brought into breeding condition on sinking wafers, frozen blood worms, several different kinds of flakes, and occasionally freeze-dried and frozen adult brine shrimp. The parameters of this aquarium were exactly the same as the aquarium they were in previously. For some reason there was a plastic livebearer breeder trap sitting in this aquarium. I have no idea why, as there was never a fish in it.

Anyway, this was the chosen site for the C. pygmaeus to deposit their eggs. It was covered. Unfortunately I did not witness this spawning, just found the eggs. The eggs seemed slightly smaller than those of the other Corydoras that I have raised, but developed the same way.

First a dark line appeared, and as they aged it got larger and darker, and they hatched and the fry dropped to the bottom. Their first food was artificial plankton rotifers, as they were too small to eat the baby brine shrimp. This was fed every three days, and a 30 percent water change was done every three days before the new food was added.

Water changes have to be done very carefully with a hand siphon so as not to pull the tiny fry out. This still happens, however, and most can be put back in with an eye dropper without causing them any harm. This can sometimes cause problems with broken backs or other damage, where the fry end up dying, so it is best to take it slow and easy and try not to pull them out.

After two weeks they started to eat the baby brine shrimp, so the artificial plankton rotifers were stopped. With the baby brine shrimp, 50 percent water changes were done every night. At the four to five week stage, flakes and sinking wafers were added to their diet.

These little fish had dark broken lines and looked more like C. habrosus than C. pygmaeus until they were seven weeks old. That is the time when the solid line showed up and they looked just like their parents.

Persistence Wins Out

Sometimes persistence pays off, and so does doing lots of research. However, in the end it was just some good luck and a plastic livebearer breeding trap.

These are very nice fish to add to a community aquarium, as they are so peaceful. The only problem is to remember that they can only be housed with smaller fish, such as small tetras and rasboras. I accidentally put six young angelfish in with some and let’s just say they angelfish were definitely not angels, they thought these little cories were a tasty treat. I removed them quickly to save what was left. Beginners do make mistakes—but I quickly learned from mine.

Posted June 2nd, 2015.

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