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Randy's Aquaria Logo

Spawning and Raising Tetras, Barbs, and Rasbora

An initial draft for a talk delivered by Randy

- Randy Carey -

Cichlids spawn themselves. If you want a real challenge, a notch in your breeder's belt, try a fish that requires you for breeding success. "You will feel more satisfaction than when your Angelfish spawned and gave you fry."

For some reason, most of today?s aquarists don?t try to spawn the egg scattering tetras and barbs. Most aquarists start their spawning experiences with fishes that show parental care, like the cichlids. And most of those hobbyists never move on.

In my fishroom, I work at spawning the egg scatterers. Meanwhile, in the background, I let the cichlids spawn and rear their young. As I write this, I have eleven species of cichlid fry, but I only worked at one. Conversely, I have fry from four tetras, a barb, and a Rasbora. Each one of these required that I play an active role in conditioning, inducing spawning, and rearing the young fry. I feel the proudest of my tetras and Rasbora spawns. I feel the most satisfaction when I know I have a batch of fry that one just doesn?t get by leaving the fish on their own.

But I don?t want to frighten you into thinking egg scatterers are too hard. Several species like the Black Tetra and Flame Tetra are easily induced to spawn. You just have to be an active player in setting up a spawning tank and raising the fry on baby brine. Believe me. The first time you succeed, you will feel very proud. You will feel more satisfaction than when your Angelfish spawned and gave you fry.

Basic Reproductive Pattern

I've succeeded dozens of times.

Here's what to expect ...

The reproductive cycle of most egg scatterers follows a basic pattern. After being fed well and kept in good water, the male will start to chase the female. Eventually the female becomes cooperative and the pair spawn side-by-side, usually scattering several eggs at a time. When done, the adult fish start thinking of food and scavenge for the tasty eggs. Usually, the aquarist must have a set up which prevents most of the eggs from being eaten.

The eggs are like crystal balls, either clear or amber. I don?t think I?ve ever seen these eggs with a diameter bigger than 1/16 of an inch?often they are smaller. The eggs hatch usually after one day, but sometimes two. The fry are not wrigglers. They cannot swim. They lie on the tank floor, and if a light hits them, they jerk up an inch or two into the water and coast back down. In two to three days, after the egg sac is about all gone, the fry attach themselves to objects so that they hang vertically. Often you can see them as slivers of glass hanging on the sides of the glass.

In less than 24 hours of hanging, they begin to freely swim. This is when they are looking for their first food. According to most literature, most of the smaller species are unable to eat baby brine the first day. But I have seldom had to go more than two or three days before the baby shrimp is received. You can tell they are eating it from the big orange bulge of a single shrimp. From my experience, I feel I am past the critical stage once the fry take baby brine.

Colors and markings usually begin to appear during the fourth or fifth weeks of life. As with any generalized pattern, the events and their timing varies. Some tetras are internally fertilized and a few guard the spawning site. I have found that the so-called "splash tetras" lay their eggs on leaves, the eggs hatch after 2 days, and the fry hang almost immediately. Still, the pattern I?ve outlined is the norm for most tetras, barbs, and Rasbora.

Conditioning

Your first responsibility, should you dare chose to try, ...According to the Baench Atlas, only a few tetras will spawn without conditioning on live foods. While I offer flakes, most feedings are based on daily squirts of baby brine shrimp and an occasional feeding of black worms. The larger the fish, the more I rely on black worms. All but some of the large barbs and tetras (over 4 inches) greedily consume the baby brine shrimp.

The conditioning tank should be conducive to good health and the development of viral eggs. Yet, because I want to trigger a spawn, the conditioning tank must somehow inhibit the fish from spawning. I want to the pair to find the spawning tank conducive to spawning. I can hold the pair back one of three ways. I can separate the pair. I keep the fish in a community tank which is too distracting to the fish. I can keep the conditioning tank?s water outside of the ideal parameters (temperature, pH, hardness). I prefer the first two.

Pick A Pair

You only need two, but you better get the right two. Yeah. Picking a pair is not always easy with tetras. Sometimes they look so similar. But there are some tricks. As in many other fish groups, sometimes the dorsal fin (or even the caudal) is longer in the males. For example, Red Phantoms, Copella, and Congo Tetras vary by finnage.

The most common dimorphism is the anal fin, and for two reasons. First, the males of many tetras have tiny hooks on their anal fin which often get caught in a net (Swordtail Characin and a host of others). Secondly, the shape of the fin (concave vs. convex) is a very common feature (from many Pencilfish, to darters, to many tetras). Unfortunately, the difference in shape is not easy to recognize. Sometimes coloration will tell. The color of the adipose fin is a sexual dimorphism in the Black Phantom and the Kerri Emporer Tetras. Eye color distinguishes the three Emporer Tetra species. The best all round technique for determining a female is the bulge in her belly when fed well. This technique applies to almost all tetras, barbs, and Rasbora. If you aren't sure, capture some fish in a net or a bag and look straight down. Often you can see a bulge distinguishing the females which are ready to spawn.

But as I will repeat in this article, check the books and articles on a species for tips. Sexual dimorphism varies per species. I recommend any and all of the Baensch Atlas. In particular look at volume 2 (pages 192-3) which portrays the dimorphism of ten tetra species.

Spawning set up

Here is where the fun begins ...

The aquarist tries to accomplish three things in the spawning tank:

  • [1] induce the pair to spawn,
  • [2] keep the spawners away from the eggs, and
  • [3] keep the eggs from fungusing.
[Spawning Tank Set-up]

1. Inducing a Spawn

Of the three goals just listed, inducing a spawn is usually the most challenging. In the previous ten weeks, I have set up thirty-some spawning tanks and obtained eggs in eight of these attempts. Realize that many of the species with which I?m working are challenging to breed, such as the Rasboras. But the point I want to make is that despite doing everything right, many attempts will fail to produce eggs. Like a baseball player at the plate, sometimes one just has to try several times before getting a hit. The goal of the breeder is to do what it takes to increase one?s average of success.

Water Parameters

The most important thing to raise the chance of a spawn is the water quality and its parameters. Aquarists before us put much importance behind pH and hardness. In general, the groups of fish I?m talking about require soft and acid water. From my experiences, most barbs prefer a pH from 6.5 to 7.0 and require some general hardness, such as 2 to 6 degrees, but little or no carbonate hardness. Recently, I attempted a Barb spawn in 5.5 pH with mostly r/o water. The male lost his coloration and the pair showed no interest in spawning. Throughout the course of about ten days, I incrementally added tap water (dH 15) to raise both dH and pH. The pair spawned once the pH had just about reached neutral and the dH was about 6.

Tetras are a very diverse group and their breeding requirements span the range of almost pure water with a pH well in the 4?s to relatively hard, neutral water. In general, most aquarium literature and my experiences suggest a pH in the low 6?s with a dH around 2 is satisfactory.

Rasbora species are supposed to be a difficult fish to breed. Not until recently have I observed my first Rasbora spawn. My Scissortail Rasboras first showed an interest in spawning after I changed their tank to nearly all r/o water and once the pH had drifted down to 5.0! I transferred them to a spawning tank with water of the same parameters and had success. I proceeded my attempts with three other Rasbora species and obtained eggs from two of the three. In each case I used 100% r/o and the pH was in the 4?s. I kept Rasbora maculata in the spawning tank for over a week, and they spawned once the pH fell to 4.4! My currently theory is that Rasbora are seldom bred because their spawnings require such extreme water parameters.

These are my generalizations regarding the pH and hardness of these fish groups. I recommend one checks multiple sources for the species he/she wants to try breeding. Recommendations will vary, but they will give you an idea of what to try. Of course, temperature is important. Once again, you ought to check with aquarium literature for specific recommendations per species. In general, I shoot for 78 to 83 degrees and I prefer submersible heaters.

Another factor is water additives. I have had success using 100% r/o water with Black Water Extract or Waters of the World additives. Since Waters of the World is buffered, sometimes I use a bit of it with a drop or two of phosphoric acid to adjust the pH to a target value. Some, not all, of these species come from black water streams. In theory, these additives provide some natural elements which can trigger a willingness to spawn.

I am convinced that triggers do exist in at least some species?perhaps in most. One day I came home with some plants that had just come in from a commercial grower. The plants were still in the grower?s bags. I put these bunch plants in the tank and within a couple of hours I witnessed three tetra species starting to spawn in a community tank. I immediately set up spawning tanks and obtained eggs from the Serpae and Lemon Tetras. Then I transferred some of these plants to another community tank. Again within a few hours, I observed four month old flame tetras scattering eggs in a pH of 7.8! I am convinced that some mineral or organic element came from the plant and stimulated my tetras into spawning.

Other Factors

Some aquarists claim other factors contribute to successful induction of spawns. Conductivity is related to hardness and may play a role. I?ve read numerous postings from amateur aquarists that a drop in barometric pressure sparks spawning behavior. But is this is first hand experience or just repeating what one hears? Willy Jochner, author of the classic series Spawning Problem Fishes, reported that with some species he was more successful with spring water over rain water or distilled water. What is it in this water that made a difference?

In nature, often species are induced to spawn seasonally. The trigger could be simply a set of certain water parameters. Perhaps the more difficult species require a sequence of several things before their trigger is pulled. Some seemingly impossible tetras like the Bleeding Heart probably require this seasonal sequence of conditioning. Unfortunately, I?m not sure what the triggers are or what patterns exists. I will only discover this by journaling successes and failures, and ?98 is my year to start a rather thorough journaling of my spawning attempts.

Plants in the Spawning Tank

I have had much luck spawning tetras and barbs in a tank without plants. However, I tend to think that the addition of a plant or spawning mop is beneficial in getting eggs. Perhaps it just makes the fish feel more at ease since they spend most of their lives in the protection of plants. Often I find most of the eggs scattered-but-grouped around a small Java Fern. This suggests that the fish found some reason to spawn near the plant. Perhaps in many cases, the spawn would not occur had the plant not been there. Just in case, now I usually provide a four to six inch high clump of Java fern (well washed to avoid introducing debris).

Indeed, some species require plants. I once gave up on a pair of Checkerboard Barbs so I removed them from the spawning tank and put them back into a community tank. Within hours I saw two pair of this species spawn in the plants. As it turns out, the female lays one egg at a time, and each egg is deliberately placed in a bushy plant. I suspect they didn?t spawn earlier because I didn?t provide a suitable plant for the female.

Let There Be Light

Most tetras and barbs are stimulated by the morning light. For instance, Beckford's Pencilfish have been observed to follow regular spawning sequence corresponding to the morning light. Aphyocharax rathbuni have been noted to spawn only in the morning. The breeder is wise to simulate day and night in the breeding tank. This is natural and it seems to be benificial. I usually use an under-cabinet 15-watt fluorescent light. The light is often turned so that it shines indirectly into the tank. I feel a glaring light might disturb the fish and could start eggs to fungus. Recently I got eggs from Red Phantoms but only after I forgot to turn the bright light on one day. I assume the light was too bright. Afterall, many species come from dimly lit jungle streams.

In some species, night is supposed to stimulate spawning. I've read that the Rummynose Tetra spawns at midnight. While I have recognized distinct morning and distinct evening spawners, my experience have yet to demonstrate a night spawner. In short, cycle through day and night with a light, and experiment with how bright you keep it.

It Starts With Conditioning

I?ve just discussed making the spawning tank conducive to spawning. But I want to remind the breeder that a willingness to spawn starts with conditioning in quality water and with quality foods?usually live foods. Remember that with egg scatterers, the goal is to induce a spawn in the spawning tank with its special set-up for capturing the eggs. This means that the fish must be discouraged from spawning prematurely in the conditioning tanks. Then the transfer to the spawning tank will have more impact.

I see three ways to discourage spawning while conditioning. [1] isolate the males from females, [2] condition with several other species so that a pair is distracted by all the activity, and [3] maintain water parameters which are just outside those needed to induce this species. For any of these three means, a transfer from the conditioning tank to the spawning tank creates an encouragement to spawn.

[Spawning Tank Set-up]

2. Protecting the Eggs from the Parents

The second objective of a spawning tank is to protect the eggs from the adults during and after the spawn. Few egg scatterers defend their eggs. Usually they are so involved in the spawning act that they ignore the eggs until the frenzy subsides. But sometimes they will take just a few seconds between spawning acts to consume those eggs which are readily in view. Almost all will avidly hunt for and eat eggs once the fish are done spawning. Additional fish which are not involved in spawning will gratuitously pounce on the eggs, even as they are still falling.

Various Methods to Capture/Protect the Eggs

One technique is to cover the bare bottom of the tank with a thin layer of gravel. The eggs will usually roll between the pieces making them harder to be reach. The jagged and endless pattern of small stones hinders the adults from seeing them easily. Perhaps an improvement on this method is the use of washed marbles to cover the tank floor. With the uniform curved shape of marbles, most eggs will roll down into a gap and fall out of reach.

Another method which produces limited results is the use of a thick plants (usually Java Moss or Spanish Moss) on the bottom. Again, the eggs usually fall out of sight and reach. This approach offers a couple of advantages. The plants provide biological filtration, so the parents can be left in the tank for a long time. This helps for species which lays just a few eggs over several days like the Emperor Tetra. The plants also harbor the small first foods to feed the young fry. The tangled fibers of moss provide refuge and cover for the fry. Nevertheless, if the adult fish know that the bottom harbors food, they are apt to hunt for what they can find.

Unfortunately, each of these methods have the disadvantage that the aquarist often cannot tell when a pair has spawned. He/she is less apt to know when to remove the parents and when to provide first foods (though this is not as critical with the Java Moss method). If the pair is left for even one day after the spawning, the eggs will hatch and some fry will probably jerk up into the water, drawing attention to themselves. After finding just one or two of these moving snacks, the parents will start hunting for more and keeping a close eye out for any movement. I have known four people who have had success with the "moss" method, but the success was quite limited. Though fry are obtained, only a few survive?even when the species is known to lay one hundred eggs or more.

Interesting Experiences

Before I describe my preferred way, I?d like to mention three previous experiences.

One time I transferred the tetras of a community tank to a new-but-temporary set-up of a 20 long. The fish were in it only a day before I moved them out. I didn?t tear down the temporary tank right away. The next day I happened to see tiny fry bopping up out of the gravel. I grew them up and they turned out to be Red-Eyed Tetras. The fish had spawned in this crowded 20, but a good number of eggs fell between the gravel. Had I not moved the fish back out of the tank, the occupants would have devoured all fry and I would have never known. A similar experience occurred with Zebra Danios, twice. The four to six inch male Pink Diamond Tetra, Rhodsia altipinos, guards the spawning site. One day I saw the male defending the gravel at one end and all of the other fish cowering at the other end. With a flashlight I saw the newly hatched fry amidst the clutter of the gravel. I merely removed all adult fish (including ?dad?) and grew out over 100 fish.

I implemented the most unorthodox method of obtaining eggs when my Checkered Barbs spawned. I saw them laying one egg at a time in fine feathered plants. Other fish would follow and gobble up any eggs they could find. I got out my baster and gently moved the plants. Whenever I saw a small crystal sphere falling, I would sucked it up with the baster and then eject the catch into a small quart container. I captured nearly fifty eggs in two hours and over half of them hatched in that small container!

My Preferred Method

Serious breeders of this fish group use spawning screens (also called "nets" or "traps" ). These are "engineered" to fulfill the intent of the spawner. They allow the eggs to fall our reach. Furthermore, the aquarist can observe when the spawning has occurred, estimate how many eggs have been layed, react in a timely manner to the needs of the eggs/fry, and observe egg/fry development.

Although what I use as a spawning trap has changed, this is the method I employ when I attempt to obtain a spawn. It has allowed me to obtain over a hundred eggs for many species (and over a thousand for the Scissortail Rasbora). I enjoy seeing the eggs and watching the first week or two of fry development. I find this as one of the best pleasures of the hobby. After all, I?m not breeding to farm fish for sale, rather I breed for the challenge and the marvel of the experience.

Originally I used bridal veil material as my netting. Glass rods weighted with granite would hold down the edges and a piece of plastic plant would be placed in the middle to lift the net above the tank floor. This usually worked well, but I had to work hard at getting the net just right so that the fish couldn?t get under it (as sometimes they did). Recently I improved on this method by building a better spawning trap. In short, I start with a plastic grid of the egg crated material used to diffuse light in fluorescent light fixtures. I cut plastic seining net material and fasten it over the plastic grid with synthetic yarn. (The yarn must be synthetic or else it will deteriorate in the water.) I cut four equal-length pieces of pvc tubing, usually about one and a half inches long. These pieces are used as legs in the bare tank to suspend the spawning grid above the tank floor. The height of the legs allows me to observe fallen eggs. Finally, I use precisely-cut thin pvc tubing to cover the gaps against the grid and the tank sides. I am very pleased with my new traps. I have build five for ten gallon tanks and one for a twenty-long.

[Spawning Tank Set-up]

3. Preventing the Eggs from Fungusing

I have not conducted my own experiments, but I listen to tetra breeders who have gone before me. They claim that the tank should be as free from bacteria as possible and that the eggs should not be exposed to much light. I know that this is not always the case in the wild, but my tank is stagnant, so I take the extra precautions. Almost always when I start a set up, I bring the ten gallon tank to the sink and clean it with vinegar. It is a mild acid which seems to disinfect. I rinse the tank a couple of times to remove any residue of the vinegar. Sometimes, when a pair hasn?t spawned for a number of days, the tank floor seems clean enough so I forego the washing.

I will testify that I and others have had success in tanks which were far from clean. However, I?ve read that the eggs of some species require minimal bacteria to develop. To lay it safe, I regularly clean the tanks.

Let There Be Darkness

Once I have observed eggs, I watch the adults to see if they are still in spawning mode. When I feel that they are finishes, I remove the parents, remove all spawning paraphernalia (unless they have adhessive aggs sticking to them), and darken the tank.?the light is turned off and the tank is shrouded with a towel. Again, multiple sources claim that light can cause eggs to fungus. Perhaps I need to experiment with this, but right now I play it safe.

When eggs are first laid, they tend to be clear or amber. They may turn slightly milky as the fry develops. New born fry often appear milky white until they hang vertically. If they turn a fairly harsh white, the eggs have fungused. If all the eggs you see have this look, wait it out for a couple of days. Sometimes fry will emerge from unseen eggs. After all, good eggs are nearly transparent and white eggs are far more noticeable.

I have used funguscide products and general ones like methyline blue or acriflavin. Lately I have not used these. A good, healthy batch of eggs seems to do all right without them . Besides, I want the fry to live in chemical free water as they develop into free swimmers and start searching for their first food. If I have repeated problems with fungused eggs for a species, I will try something chemical preventative.

The eggs hatch usually within 24 hours of being laid, but some species take as long as two days. At this point I have cleared two hurdles: getting a spawn and hatching it. (Getting the spawn is the most challenging.) Now I am faced with the third and final hurdle: getting the fry to the point they can eat baby brine shrimp.

Newborn Fry: unable to swim or eat

I leave the tank dark until the fry become free swimming. On the first couple of days, most tetra and barb fry will jerk in reaction to the beam of a flashlight. I often see them concentrate more away from the lit end of a tank. I assume that in this phase of life they prefer to avoid the light. Since they don?t eat until they are free swimming, I just keep it dark. Once the egg sac has nearly been consumed, the fry attach vertically to something?again, often away from the light. If I have removed all plants and other objects from the tank, the fry will inevitably scatter themselves along the sides of the tank. From time to time, a fry will detach and relocate?similar to how a human stirs in his sleep. While they are hanging, they are relatively easy to see (with a flashlight). This is a time in which I can estimate their numbers.

Usually the fry are done hanging within 24 hours. Instinctively they hover near objects for cover. Most tetras and barbs like to congregate next the silicon seal along the tank?s bottom. Given their color, they can be hard to see. At times I could swear I had only six or eight, but as the tiny fish grew, I would realize that I had a few dozen. Be forewarned. At this stage you may feel like you failed when you just need to give it time.

First Foods

Once the fry become free swimmers, they are looking for food. If the fry are large or aggressive enough, you may be lucky and they will be able to take a baby brine shrimp right away. Remember, all tetras are born with teeth, and some species are so determined that they capture and shred a baby shrimp to eat what they can. These tetras include the Head-N-Taillight and the Glowlight.

If the fry won?t take baby brine shrimp right away, you will have to provide smaller foods. The older books suggest infusoria which the aquarist must culture. Other sources of micro-organisms are plants (Java Moss) and sponge filters. Actually, most items in an established aquarium harbor these tiny animals. Live micro-foods seem to be a requirement for fry which congregate at the top (Pencilfish and most Pyrrhulina). However, most tetras and barbs seem to hover just off the bottom. I have found microworms to be the surest way to guarantee that I can provide ample food. I feel the fish can grow faster on microworms than on micro-organisms.

As the fry grow on the smaller foods, I will periodically try baby brine shrimp. Once I see orange in some of the bellies, I celebrate. I will continue the smaller foods for another day or two along with the baby shrimp. This helps the slower growing fry to reach the point that they can eat baby brine shrimp. With only a very few exceptions, young fry need only a day or two on small foods before they can take baby brine shrimp.

My characin friend, Pete Peterzen, claims that all of his tetras always start off on baby brine shrimp (bbs). However, his spawning method is to use a thin layer of gravel and remove the parents right away. My feeling is that the young fry find plenty of micro organisms in the gravel. So while the first food he gives is bbs, they actually are eating before they can take bbs.

Closing Remarks

I have just given a generalized discussion of what it takes and what one should expect in successfully spawning and raising tetras, barbs, and Rasbora. Remarkably, the species of these groups possess very similar spawning patterns. Still, the aquarist ought to research a species before starting. For instance, no Neon Tetra fry will survive if the dH exceeds 4, and a dH of 1 or less is ideal. Another tetra, Hyphessobrycon scholzei, readily spawns in water with a pH up to 8.

I recommend any of the Baensch Atlas books. Many of the older books have great information. Of particular interest is Willy Jochner?s two book set "Spawning Problem Fishes." I believe it is out of print, but it does surface from time to time at used book stores.

Although the fishes from the Pencilfish family (Lebiasinidae) are more closely related to the true tetras than are barbs and Rasbora, I have come to expect different things from the spawns Pencilfishes, Pyrrhulina, and Copella. But my recent experiences with these species is fodder for a future article.

As I said earlier, my greatest pleasure comes from spawning and raising species which require me to be involved in order to get success. Cichlids are nice and their fry can be somewhat profitable. I still keep and spawn the dwarfs. But my breeding has moved on from these easier fishes. I prefer breeding new species which are more challenging and more rewarding. That?s why I work at spawning and raising tetras, barbs, and Rasbora.

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