Homegrown Food - Nourishing Nematodes
What are Microworms? Microworms are a group of nematodes in the genus Panagrellus from the family Panagrolamidae. So, a better question might be, what are nematodes? Nematodes are phylum of creatures called roundworms, many of which are transparent and microscopic.
Despite being hard to see, they are found on every single continent – including Antarctica. Nematodes are hard to distinguish from one another, so there's a decent amount of controversy surrounding how many species there actually are. Estimates range from 25,000 different species to some suggesting as many as 100 million. They are one of the most common forms of life on this planet from the top of mountains to the bottom of the ocean, nematodes exist even in rocks and deep under ground with an estimated 60 billion individual nematodes for every human living on this planet, and 80% of the total living animals on this planet are nematodes! Some nematodes are parasitic, but the good news is that of the at least 25,000 different species of nematodes only 35 species are found in humans, and luckily for us, the ones that we culture as a nutritious aquarium food are not parasitic at all! The most common Nematodes available in the aquarium hobby are Banana Worms, Walter Worms, and Microworms. These are popular live foods for several reasons. They are easy to culture and nutritious, making them great live food for fishes too small to eat baby brine shrimp. Microworms grow quickly to their maximum size, ranging from one to three millimeters depending on the species, and attain maturity at around four days old. We will talk about the three most common varieties of microworms and then explain how to setup a culture for them next!
Banana Worms (Panagrellus nepenthicola) are the smallest of the three species. Being so small they are frequently the first choice when considering what to feed a fish too small for brine shrimp. Growing to only 1/16th of an inch or 1.5 millimeters these nematodes reach sexual maturity at about 4 days of age and will produce about 60 young per day for the rest of their lives (which last for about 35 days). Their desired temperature range is between 70 and 80 degrees Fahrenheit but a few degrees in either direction of that wont hurt them. Banana worms grow faster than Microworms – and a colony can be split or fed out of after as little as four to seven days after making it.
Walter Worms (Panagrellus silusioides) is the second largest species of microworm. Having three different worms with slightly different sizes can help the aquarist by allowing them to pick the biggest possible food that’s easy for whatever size fry you are trying to feed. One interesting fact about Walter Worms is that this particular species of nematode was not described until 2002 – making this species relatively new. While Walter Worms are smaller than Microworms, their nutritional value if cultured in the same way is virtually identical, so the only difference really between these is size. They attain maturity at around four days old and have similar reproductive rate and lifespan to the Banana and Microworms.
Microworms (Panagrellus redivivus) are the largest of these three species of nematodes, and probably the most popular or commonly available in the aquarium hobby for that reason. Humans share a lot of space with Microworms – which are also known as beer mat worms from living in constantly wet felt once commonly used in bars. They are also eaten by humans as part of yeast fermented rice which will frequently be colonized by these harmless nematodes. Microworms grow to sexual maturity in only three days, and give live birth rather than laying eggs like most of the other nematode species we have discussed.
Culturing all of these nematodes is very easy, and they make for a great beginner food culture. Many freshwater fish fry such as bettas will hatch out at a size too small to be fed baby brine shrimp, which is where having nematode cultures will come in handy. Cultures can be made in any size container but generally you will see them in plastic containers in sizes ranging from a sandwich to a shoe box. Poke a few small holes in the top to allow air flow, but fill these with filter floss or cover the culture with a paper towel before covering with the lid to prevent other things from making their way into the culture. Pour about half an inch of unflavored instant mashed potato mix into the bottom of your container, and add warm water and mix it in until it reaches a wet, but not runny consistency. The medium shouldn’t pour when you tilt the container but can slowly move, so slightly wetter than actual mashed potatoes. Wait for this mixture to cool down to room temperature, and add a generous spoonful of starter culture to the new one. It should begin to produce for you in a week, and last up to a little over a month. If the culture starts to smell especially bad, get darker in color, or get growths of any type in it, its probably time to move on. Starting new cultures regularly insures that you will always have healthy live food available for babies or small fish in your collection.
Harvesting the worms is easy – you will know the culture is ready when worms start to crawl up the sides of the container. Harvesting is simply removing worms from the side and adding them directly to the aquarium. Some people use their finger, others use a paintbrush or q-tips. No wrong answers here and the worms essentially clean themselves of the media as they move up the walls of the container, so there’s no need to rinse them as you would have to do with brine shrimp. Any of these three species will survive in water for up to twelve hours, so the fish should have a long time to make sure there is no waste, but still take caution when portioning out live food.
All in all, Micro/Banana/Walter “Worms” aka nematodes are an easily cultured, nutritious live food source for small fishes or young fishes that aren’t big enough for some of the more standard live starter foods. Larger adult fishes that are still small such as Endler's Livebearers, small Tetras and Cories will also relish these as an occasional treat. Ask your local fish club or fish store to help you source a starter culture today!