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Jan 19

Raising the fry

Raising the fry – hints and tips to grow many healthy fish

kribensis mother guarding newly free swimming fry

kribensis mother guarding newly free swimming fry

If you have successfully gotten your fish to breed and now have a large batch of eggs or even a population of tiny fry living in your tank, it could be time to brush up your fry-parenting skills. You may need to adjust your approach depending on the exact nature of your specific species of fish, but the basics of caring for fry are largely universal in nature.

Newborn fry are very small and delicate creatures, and you will have to concern yourself with their health and safety if you want to see them grow into healthy adult fish. There are a few basic requirements needed for just about any species of fry to successfully grow:

Clean water-Your fry might need you to perform water changes much more frequently than you are used to. They are much more sensitive to changes in water conditions than their parents are. Small frequent water changes are best. The fry also grow faster when in clean water. Betta fry are notoriously slow growers when less water changes take place.

. Filtration- Your spawning tank should have a high quality sponge filter or two. Don’t be afraid to have several sponge filters in the same tank. Sponge filters usually have microscopic life attached to them that are growing on the filtered waste matter. Fry will pick off and eat these micro organisms adding to their diet. The slow flow rates from the sponge filters are much safer for fry than faster powered filters.

Separate tanks-Fry are a quick snack to most fish. Even some cichlids that protect their young on occasion will eat their own fry. You will need to keep your fry safe in a separate tank or you will have to remove all adult fish from the breeding tank. Have several containers ready for when the fry grow. Also, some fry will grow faster than others, and the larger ones may eat the smaller ones.

free swimming killifish fry hover near the water's surface

free swimming killifish fry hover near the water’s surface

• Closely covered tanks-Some species where the fry live at the surface of the water or breathe in oxygen from the surface such as anabantids are harmed by draughts. A tightly fitting lid will prevent cold draughts from harming these fry.

• Microscopic and tiny live food-Fry usually need to eat live food. The main choices are explored below. Determining the right food for your fry is critical.

• Anti-fungal and anti-bacterial chemicals—Fungal and bacterial infections can destroy good batches of eggs and fry. Methylene Blue and Malachite Green are two good options that can help protect your spawn and fry from sickness and infection. Add as soon as the eggs are laid in not too heavy doses. Perhaps half normal dosage is good. Malachite is copper based so care has to be taken with copper sensitive species. Methylene blue will harm live plants.

What to feed your fry

You are limited to a select few choices for feeding fry. These include infusoria, baby brineshrimp and microworms, which are the most common choices. Generally, the best option is to raise your own live food when possible. Most species’ fry will only eat live food.

These foods need to be ready before your fry become free swimming and start eating. They also need to be staggered. You will need to have a fresh batch started on a daily basis.

Each option represents certain advantages and disadvantages, especially for certain species. For instance, Anabantid fry will be too small to eat baby brine shrimp, requiring you to feed them the tiniest possible food: infusoria. Other species, such as Angelfish, can often be started on larger food sources such as baby brineshrimp and infusoria. But sometimes large species created tiny fry. Also as the fry grow, some will grow faster than others. Some of the fry will only be able to eat infusoria while the larger fry will need baby brineshrimp

Since infusoria are the smallest possible fry food, it may seem reasonable to simply start there and then move on to other foods when the fry have grown large enough. While it is a reasonable plan, infusoria do come with a drawback: being microscopic, you cannot really be sure that your fry are eating. Only after the fry have finished feeding will you be able to see the fry bellies fill up and colour up from eating infusoria all day.

Baby brine shrimp represents one of the best choices for feeding those species of fry large enough to eat them. They are easy to raise and offer the most complete nutrition for your baby fry. These tiny shrimp will live for up to five days in freshwater, giving your fry enough time to catch and eat them while they grow. The great advantage of baby brine shrimp is that they do not add infections to the aquarium.

Frequent feeding will help your fry grow more quickly; some aquarists suggest small meals 3-6 times per day. Fry tend to have shorter intestinal tracts than their adult counterparts and so are more carnivorous as well. They don’t eat algae but do eat the creatures that eat the algae. If you find yourself in a pinch and need to feed your fry quickly without having access to brine shrimp or infusoria, you can use hard boiled egg yolk. Squeeze through a cloth into the aquarium to create a cloud of fine particles. The biggest drawback is that egg yolk quickly rots and pollutes the aquarium. You must siphon off carefully all uneaten egg particles.

Culling your fry for a healthy brood

One of the critical steps of raising a successful batch of fry is culling the weak and deformed fry early on. Unless you have an exceptionally large aquarium for all of the fry to grow in, you will need to cull the brood. Culling consists of removing all but the strongest individuals from the tank in order to maximize their chances of success at the expense of their weaker brethren. If you don’t cull then overcrowding will do the culling for you, with perhaps all the fry dying through lack of space.

Very few aquarists are equipped to deal with the hundreds of new fish that an average spawn can produce, and indeed most natural habitats cannot support such large populations either. As a result, culling takes place, either by your hand or by the nature’s hand leaving only the strongest members of the brood alive.

Generally, you want to perform your first culling as soon as the fish become free swimming in order to remove any deformed fish that obviously have no chance of survival and leave as much space and food as possible to the stronger ones. Later on, as certain individuals do well and other ones begin trailing behind, you will need to continue culling. Any fry that have not developed all their fins properly, have deformed spines, are not completely symmetrical, have swim bladder problems and are stuck to the bottom or float must be culled.

The most natural way to cull fry is to feed them to other fish. This is exactly what would happen in the wild and is the reason most fish produce hundreds of offspring in the first place. Some aquarists prefer freezing or other humane methods of culling, but the result is the same—just don’t flush them down the toilet.

Life stages: caring for your fry through to adulthood

Many fry will go through specific life stages on their way to adulthood. In the case of Malawi cichlids, for example, you will find that fry are first born with rather large yolk sac attached to the body. These types of fish will spend about 21 days or more, living off of the yolk sac while inside the mother’s mouth.

Malawi cichlids are mouthbrooders whose fry will generally be large enough to begin eating dried food as well as live food after birth. Livebearers are about as large as Malawi fry and the same goes for them. The dried food may need to be ground into a powder first however. Most other species need live food: Tetras, for example, are egg scatterers whose fry will slowly consume their own yolk before becoming free-swimming fry, at which point you can begin to feed them baby brine shrimp for the larger species but usually infusoria if they are too small.

5 week old kribensis fry

5 week old kribensis fry

For most species it will take at least 1 month before the fry actually look like miniature versions of the adult. And it takes even longer before they take on adult colours. In many species the male and female young will look like the adult female until quite late into development. At this stage the fry are reasonably hardy and can be cared for like the adults.

After some time, you should notice your fry getting significantly larger and livelier, and it may soon become time to introduce them to a new tank. A common indicator that your fry are ready to move to a new tank can be seen in their colouring. Fish that already exhibit their adult coloration and have begun behaving more socially can often be safely moved to a community tank. To be on the safe side make sure that the juveniles are bigger than the biggest mouth of the fish in the community tank, including the catfish. Remember the rule no matter what fish you have; if a fish can fit in the mouth of another fish, sooner or later it will be eaten.

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