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Breeding fish is such a fun and rewarding part of the aquarium hobby, but while it can be easy to get fish to spawn, raising their tiny babies is where the real challenge begins. High losses often occur in the newborn phase because of water quality issues, predation, or simply not feeding enough of the right foods. In this article, let’s talk about 5 miniscule foods that you can feed even the smallest fry to help them grow quickly and get past the first few weeks of their lives.

1. Baby Brine Shrimp

Peacock gudgeon fry eating baby brine shrimp

If you talk to veteran breeders or fish farms that produce massive numbers of fish, they know that the #1 best food to feed fry is baby brine shrimp (BBS). Newly hatched brine shrimp have a nutrient-packed yolk sac that is chock full of healthy fats and proteins — perfect for feeding baby fish. As a live food, their jerky swimming movements also entice the fry to eat more so they grow faster and stronger. To hatch the brine shrimp eggs, simply soak them in salt water, add aeration with an air pump, and heat the water up to 74-82°F (23-28°C). Within 18–36 hours, the baby brine shrimp are ready for harvesting. As long as you buy good eggs, the recipe is very reliable, so follow the instructions in this article.

Baby brine shrimp are approximately 400–500 microns in size and are suitable for many baby livebearers, African cichlids, and other species that lay larger eggs. However, if you are hatching tiny fry from egg layers like killifish, rainbowfish, and tetras, the newborns are too little to eat baby brine shrimp. Therefore, the rest of the article focuses on even smaller “starter” foods, with the strong recommendation that you switch over to baby brine shrimp after a couple of weeks once the fry are big enough.

2. Infusoria

Freshwater plankton under a microscope

In the wild, most baby fish eat microorganisms such as protozoans and invertebrate larvae ranging between 20–300 microns. Infusoria is the common name that fishkeepers use for these freshwater plankton, and there are many methods for culturing them. One of the most popular techniques is to fill a large jar with a few quarts (or liters) of old tank water and mulm, and then drop in a piece of banana peel, catappa leaves, instant yeast, or other organic matter. Warm the water to tropical temperatures between 78–80°F (26–27°C) for faster results and add aeration to minimize the smell. Soon, the water should become cloudy as bacteria breaks down the food, and then it will turn clear as the infusoria consumes the bacteria.

To harvest, use a pipette or turkey baster to suck out some water just below the surface scum and feed it directly to the fry. Depending on the size of the jar and how often you are harvesting, the culture may last 2–4 weeks. You can extend the life of the culture by topping off the jar with tank water, adding more food every week, and using a turkey baster to remove some of the decomposed gunk at the bottom. If you are raising lots of babies and need a constant supply of infusoria, you may need to start a new culture every 1–2 weeks. Just pour water from the old culture into the new jar, add a food source, and fill the rest of the jar with aquarium water.

3. Vinegar Eels

Vinegar eels being harvested in a bottle neck

If keeping infusoria sounds too time-intensive, try your hand at another live food — vinegar eels. This teeny nematode or roundworm is very simple to culture and is approximately 50 microns in diameter and 1–2 mm in length. Create a mixture of 50% apple cider mixture and 50% dechlorinated water inside a wine bottle or other long-necked container. Add some apple slices and a starter culture of vinegar eels, and wait for them to reproduce. Once you can visibly see them wiggling near the surface, harvest them by adding a wad of filter floss in the neck of the bottle and some fresh water above the filter floss. The vinegar eels will swim to the fresh water up top, so you can easily suck them out with a pipette and directly feed them to the baby fish. Their wiggling motion will attract the fry, and they provide longer access to food since they can survive in fresh water for several days. A vinegar eel culture can last up to 6 months, so follow our detailed instructions to create your own.

4. Powdered Fry Food

Hikari First Bites

If you do not have access or time to maintain live food cultures, prepared foods are an option to consider. Fry food tends to come in a powdered form that ranges from 5–800 microns, depending on the brand. The key is to provide a variety in diet so that the baby fish do not develop any nutritional deficiencies. Some of our favorites include:

Powdered foods tend to float at the surface because of the water tension, so if you are feeding baby bottom dwellers, you may need to swirl the water to get the particles to sink faster for them. To avoid overfeeding the fish, we recommend using a small children’s paintbrush. Dip the bristles in the powder and lightly tap the paintbrush a few times over the fry tank to feed them. This technique ensures that you do not feed the fry too much at one time, which can end up deteriorating the water quality.

5. Green Water

Microalgae under a microscope

Green water is very similar to infusoria in size, but the green color is more prominent because it’s primarily made up of microalgae and other phytoplankton that create energy through photosynthesis. Hobbyists are usually trying to figure out how to get rid of green water in their aquariums and ponds since it makes it harder to view the fish and plants. However, it has many benefits — such as purifying the water, making it harder for adult fish to predate on their young, healing minor ailments, and serving as a food source for baby fish and daphnia cultures. Start with a large jar, aquarium, or other container and fill it with old tank water. Add some liquid fertilizer, fish food, or other organics to create a nutrient-rich environment for the microalgae. Some people also like to use an air stone, filter, or other device to agitate the water surface and encourage gas exchange, helping to ensure the algae gets enough oxygen and carbon dioxide. Use a light source like a desk lamp to shine directly on the container non-stop for 24 hours a day. After several days, the water should start to turn more and more green and will be ready for feeding to the fry.

A Few More Fry Feeding Tips

Because baby fish have baby-sized stomachs, they need to be fed mini meals at least 3–5 times a day. Also, it helps to put the fry in a smaller container or aquarium so that they don’t need to swim as far and waste as much energy finding the food. The problem is that frequent feedings in a smaller container can quickly foul the water and cause fry mortality, so frequent, small water changes are needed to keep the water clean and stable. Master breeder Dean addresses this problem by creating a rack of fry trays that constantly drips and circulates water from a larger aquarium down below.

Feeding is just one aspect of raising healthy fry, so keeping reading to learn about our top 5 tips for growing baby fish to become big and strong.