Posted by Shari Horowitz in Tropical Fish Hobbyist Blog on November 18, 2010 at 11:01 am
By Mike Hellweg
Throughout this challenge I have had many successful spawns from egglayers—anabantoids, tetras, rasboras, barbs, danios, etc. All of these fish produce large numbers of tiny fry. These fry require tiny foods as first foods. While there are many excellent commercial fry foods available, not all fry recognize these as food and some will starve to death surrounded by what we think is the perfect food. For this reason, among many others, I prefer to use live foods.
Just as with brine shrimp and microworms, I have had to step up production for the challenge. In the past, I’ve maintained pure cultures of paramecia for first foods for egglayer fry, but these can be hit and miss unless they are maintained regularly, and they can be too large for some fry. For the contest, in order to produce a large enough quantity of tiny food on a regular basis and not create too large an amount of work, I decided to go back to what I used in the old days—infusoria.
Infusoria is not a specific type of animal, but rather a soup consisting of all kinds of one-celled and miniature multi-celled animals such as free floating algae, motile algae, ciliates of all kinds, rotifers, and more. It will vary from culture to culture, depending on the dominant life forms in your tanks. One of the great things about infusoria is that there will be a variety of critters of differing sizes and with different movement so that just about any type of fry will find something that it recognizes as food and can eat.
There are as many ways to culture infusoria as there are hobbyists who culture it. The following method works for me. I’ve used it for many years. I also asked several friends to try it while I was writing my live foods book just to be sure it would work for them, too.
Steps to Culture Infusoria
Start with a clean, sterilized jar. For the challenge I’ve been using quart sized peanut butter jars, as I have access to a large number of them. You can use anything up to a gallon sized pickle jar. Larger cultures are unwieldy and unnecessary. I start a new culture (or two) every day, depending on how many spawns I think I will have to feed. You can feed several small spawns or one large spawn from each culture jar. Fill the jar with water from a healthy, well established (preferably planted) aquarium. Some hobbyists use plain dechlorinated water, others use boiled water, but I’ve found that water from a healthy tank really gets the culture going quickly.
I add a couple of grains of boiled white rice. Boiling starts the breakdown of the cellular structure and helps to get bacterial activity off to a good start. You can use anything vegetable from rice to wheat to peas, potatoes, turnips or whatever you have available. Within hours, bacteria will begin to decompose this food source, and the animals in the water will begin to feast on the bacterial bloom and reproduce. These will become the food for our baby fish.
Depending on your particular culture animals, jars can be ready for harvest in just two to three days, or take a week or more. You can harvest as soon as you can see a grayish swarming cloud in the water column. Use a baster to suck water and critters from the middle of this grayish swarm. This can be squirted into a larger container such as a catch cup and from here be fed to baby fish, or squirt the baster directly into the fry container. Within a few hours you will see that all of the fry have bulging bellies as they are feeding. I feed the fry twice a day. Some breeders will simply dump water from the culture into the fry tank, but I prefer to have a bit more control and use the baster.
After a week to ten days the culture will begin to smell pretty nasty. For this reason, and to ensure domestic tranquility (the “alluring” scents from an infusoria culture on the edge of going bad have a tendency to seek out the one person in the household who finds them the most repugnant), I only harvest from each culture jar one time. I remove as many infusorians as possible, then clean and sterilize the culture jar and start a new culture with new rice grains, water, and a squirt of the infusorians from the old culture. Set aside a baster full of the animals and use it to inoculate a new culture container to give that a head start.
After a week or so of feeding infusoria, I will begin to mix in newly hatched brine shrimp and microworms. When I see that all of the fry have bright pink to orange bellies from feeding on the shrimp, I discontinue using infusoria.