What are infusoria?
Infusoria is a term used to collectively refer to miniature aquatic creatures that are used to feed fish fry. They are of special interest to fish breeders because they are easy and cheap to have and culture. Their small size makes them a good source of food for tiny fish fry that cannot eat Brine Shrimp or other live food. Some popular infusoria kinds are:
- Green Algae
The scientific community used the term ‘Infusoria’ to classify any micro-organisms or similarly sized creatures that lived in fresh water. Ciliates, euglenoids, protozoa, unicellular algae and small invertebrates are some groups that were classified under this category. Its usage is obsolete now and organisms that were described using this term are now classified under the kingdom Protista. However, the term has remained in use in the aquarium trade to describe only those microscopic aquatic creatures that are used to feed fish fry.
Infusoria are present in all water bodies including rivers, ponds, road-side pools or ditches. They are present in aquarium water too, but their numbers are usually not enough to sustain the fish. So, it is better to culture them in a separate container and feed it to the fry tanks as much as required. While any water source can be used to start an infusoria culture, there are two important things to consider:
- Water treated with chlorine or other reagents does not contain much infusoria and is not an efficient starting material to start infusoria culture.
- Water from outside sources like nearby ponds or ditches may contain pests like Hydra, Water Tigers, etc. along with infusoria. These pests are harmful to the fish fry and in some cases, predate on them too.
You can make your own Infusoria cultures at home easily with inexpensive starting materials. Here are the step-by-step instructions to start and maintain an infusoria culture:
- Select a plastic or glass container of up to one-gallon capacity and fill it with aquarium water. You can also add tap water, but it is recommended to leave the tap water still for some days before using it. Water from well-planted aquarium tanks is one of the most efficient sources as it contains a lot of organisms.
- Add a nutrient medium to the container. You can use a large number of starting materials as the nutrient medium which include lettuce leaves, potatoes, boiled rice, debris from an active aquarium filter, milk, grass, rabbit pellets, raw potato, yeast or commercially available liquid fry foods. The digestion waste products of Apple Snails, Columbian ramshorn snails, and some herbivorous fish are also useful in boosting the culture.
- Leave the water undisturbed for about two weeks. You can keep the container under direct sunlight to boost the growth of infusoria but it is optional.
- Once the water turns cloudy, there are enough bacteria for infusoria to feed upon. The water clears up or turns pink after infusoria consume the bacteria and can now be use to feed the fry. Examining the water with a penlight or under microscope confirms the presence of infusoria.
- After a few days, the water starts to develop an unpleasant odor. This is due to the presence of an excessive amount of bacteria. It is better to start a new culture after 3-5 days. You can use the water from an earlier source for the new culture.
Feeding the fry
The fries of the fishes like Gouramis or Betta are very tiny to eat even nauplii of brine shrimp. An infusoria culture is essential for their survival for the first week or so. Once they become large enough they can feed on other live foods or commercial foods.
The fry need to be fed many times in a day. For this, filter the culture water in order to ensure that no decaying nutrient material remains. Alternatively, carefully siphon off a portion of water with an eye dropper or turkey baster avoiding any decaying vegetative matter and introduce it to the fry aquarium. A small portion of water contains many infusoria and is enough to feed the fries. Adding excess quantity will result in the water turning cloudy and filthy. Due this will cause fry death, avoiding over-feeding and daily water changes are very important while feeding fry with this culture.