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Tips For Your Fish Room
Save Those Baby Livebearers (Part 2): Raising Livebearers

January 16, 2009

Saving the livebearer fry from being eaten by their parents is only the start of getting the fry to adult size so they can be put back into the main display tank. The next part is raising them so they grow healthy and quickly. Food type and amount are critical to raising most of the saved babies to adult size even in the baby-saver set up as described in PART 1 and illustrated in Figure 1. But these food-related factors are not the only critical parameters. When you feed heavily, the water quality goes bad, the tank bottom gets ugly, fungus can start to grow on the plants or the sponge filter, and the filter gets plugged with debris. All of these potential problems need to be addressed by those who wish to keep, raise, and proudly display their beautiful, fascinating, and home-raised tropical fish.

Livebearer Versus Egg Layer Fry

Figure 1. Red wag adults in baby-saver set up as described in part 1 of this article.

Raising livebearer fry is actually easier than raising most egg-layer fry. The advantage livebearers have over egglaying fish is that the eggs are incubated in the female's body.

The developing livebearer embryos do not get nourishment from the female, thus they have no belly buttons. They are ready to forage for food within an hour or so. In other words they are fully functional fish at birth.

Egglayer fry usually hatch with a large egg sac and are not able to swim freely. They have no need to forage until the egg sac is adsorbed after which, usually at least five days, they become free swimming. From the time the eggs are laid until the fry are free swimming, the eggs/fry are prone to attack by fungus, bacteria, and other fish as well as diseases, particularly because they are not moving. In other words they are not fully functional for a long time.

Size of Food

The deciding factor for what food to feed is the size of the fry's mouth. If you offer foods that are larger than their mouth, you will starve the fry. They might live a few days on infusoria already growing in the tank, but that results in only a few fry surviving. As the fry grow, larger foods can be added, but they will usually still take the smaller foods.

Dried Foods Are Convenient

Fortunately livebearers will take dried foods as a first food. Just provide it in a proper size. Simply crushing a really dry flake food between your fingers as you drop it onto the surface of the tank is all that is needed. If it is not easily crushed, the machines that are used to grind coffee beans are also great for grinding dried fish foods, even pellets, to a powder of a size you need.

A great initial dry fry food is CYCLOPEEZE®, because it is nutritious and already the right size for livebearer fry and it is available from your LFS. It is fed by mixing a small pinch of the material in water. Then pour the mixture into the tank, directed to where the fry are.

Overfeeding Dried Foods Can Lead to Problems

Dried foods of the right size are useful but the fry will not eat all that is put into the tank. The excess will fall to the bottom, get in cracks and crevasses and quickly start to decay. The bacteria involved in decay multiply and consume oxygen and produce waste products, which combined with fish waste help to deteriorate the quality of the water.

Bad water quality can and, particularly if allowed for any length of time, will lead to either diseases or deformities in the fry. Velvet and dropsy are two common diseases caused by poor water quality. Missing gill covers and possibly lack of a swim bladder are examples of deformities cause by environmental problems. Such deformities are thought to be the result of poor water quality particularly in the first weeks of their lives.

Live Foods Have Advantages

Live foods are much better than dried foods because the fry will seek out live food even if it stays on the bottom of the tank. The motion of the live food attracts the fry, which are visually oriented animals. Fry will eat live food until they are stuffed and their bellies are extended.

I particularly like to feed live foods for the first week or two and then introduce dried foods later. If the fry are really small, I start out with infusoria. For example, least killifish are livebearers that are very small when born and do best with infusoria as a first food. After a few days microworms or baby brine shrimp can be added. Powdered dried food can be added later, particularly as you run out of enough live food to feed.

Even with live food you do not want to overfeed. Although live foods will stay alive in the tank for a considerable length of time, most live foods will die and pollute the tank if overfed. The length of time live food will remain alive depends mostly on the oxygen content of the tank, particularly at the bottom of the tank where the excess live food will accumulate. So poor water quality can impact the time the live food remains alive. Microworms will stay alive for around a day in the bottom of a tank provided there is a good flow of oxygenated water. In stagnant water the microworms will be dead in hours.

Brine shrimp are salt-water creatures so their life in a freshwater aquarium depends mainly on the salt content. Adding a small bit of salt (up to a teaspoon per gallon) to the water can prolong the time that the brine shrimp will remain alive. But brine shrimp cannot be expected to last more than 6 or 8 hours in fresh water. And when they die, they decay rapidly. The bacterial bloom that accompanies this decay can be fatal to the fry.

How Much Food

To find out how much food is the right amount to feed, start by feeding a small amount of any food of the right size and observe the fry. If they eat all that was added quickly, you can add more. A good guideline is to feed no more than the fry can eat in four or five minutes.

To get good growth, you need to feed heavily with both dry and live foods. I find that one morning feeding and one late afternoon feeding of a good dry food mixture followed by a late evening feeding of live food will produce rapid growth. (See Figures 2 and 3.) Watch the fish for at least 5 minutes after feeding dry foods. You should not see any excess food anywhere in the tank after the 5 minutes. If you do, you should feed less.

For the live food feeding, all should be consumed in 5 minutes unless you are feeding infusoria, daphnia or microworms. If you are feeding microworms, a small excess is fine.

This article first appeared in PVAS’s Delta Tale, Vol 35 # 2.