Long known as a quality food for fish, redworms, blackworms and tubifex worms are related tubificid species, each with its own benefits and drawbacks. The question is not one of palatability–most killifish will readily take any of them–but rather one of availability and cleanliness.
Some aquarists swear by blackworms as food for their fishes; others swear at them. The relative safety of the worms is in great part determined by where they are raised. Blackworms are coldwater dwellers that prefer well-oxygenated streams or running water. In California, many are produced in the settling lagoons of vegetable processors/canners, thriving in the stagnant wastewater. On trout farms, they often grow in the cool wastewater ponds, or in the mulm that accumulates on the screens blocking the raceways. The worms are harvested when the mulm is removed periodically to maintain water flow.
Redworms and tubifex worms prefer warmer, well enriched (nutrient dense) waters with a lower oxygen content, such as stagnant lagoons and sludge ponds.
“The addition of tubifex to a daily diet of brine shrimp increases egg production of killies–almost the next day!” reports Lee Harper, then cautions, “Black worms are easier to get and keep, but I almost always have had bad experiences with fish dying unexplainedly after feeding black worms.” The incidence may be small, but it always seems to be an irreplaceable fish that dies!
Responding to this, Richard Sexton agrees, but adds that white or grindal worms seem to be as good a food for boosting egg production as are tubifex.
Health Concerns
There have always been concerns about feeding black/red/tubifex worms to fish, since the worms often breed and grow in stagnant water and heavily polluted mud. There is a long circumstantial history of disease problems in tanks where they are fed, and tubificids are known to carry and transmit a simple single segment tapeworm that is of no consequence to aquarium fish.
“Regarding intestinal parasites and black/tubifex worms: I think you have to remember that fish fed on worms eat more and therefore excrete more,” says Barry Cooper. Whether the worms are causative of disease or not, “without rigorous water changes and tank cleaning this would make the fish vulnerable to all sorts of bacterial infections.”
Richard Sexton counters this observation. “I can have spotlessly clean tanks with daily water changes but feed worms, and there are diseases that I don’t get when I don’t feed worms. This has been observed over a long period of time. On the other hand, I’ve seen fish live in all manner of …[dirt] but never get the hemorrhagic septicemia outbreaks that accompany worms,” and those oubtreaks always seemed to be proportional to the amount of worms fed.
Keeping Blackworms
Blackworms are supposedly easy to maintain and raise, with the potential of doubling the population every month or so. “Blackworms are available at my local fish shops, just not reliably,” says Steve Halbasch. “When they are available I purchase a rather large supply (up to 8 oz.),” and keep them in a 10 gal. unheated container in the basement (water temperature 60-70°F), with an airstone to keep the water moving, and weekly 30-50% water changes. To feed the worms he adds thinly sliced raw potatoes.
“Usually when I get in blackworms,” says Rodney Harper, “they go outside into several 100g PVC vats” with a substrate of local clean white sand, where they remain until all used up. “I have never had any problems.”
“I rely extensively on blackworms to feed my adult killies, probably 50% of their diet,” says Eric Lund. “I wash them every other day or so in addition to before use.” They are kept in the crisper section of a refrigerator at about 38-40°F, with plenty of water volume. “To me they are indispensable for keeping larger killies (like OCC, SJO, Pterolebias and the larger Cynolebias). As a bonus, the worms establish themselves in the planted tanks (with a gravel substrate) and provide the occasional snack as they feed on detritus in the substrate.”
“My … bad experiences with blackworms are obviously at variance with some peoples’ experiences,” comments Lee Harper. “It is just another example that there are no absolute facts in killifish keeping–only what works for you.” Lee keeps his blackworms in refrigerator trays at 40-45°F, washing them several times on the first day, then morning and evening for several days, with changes every several days after that. “I never keep them more than 6 or 7 days. [The] … worms keep well under these conditions, unless they arrive in poor shape.”
Robert Nahn maintains seven ten gallon tanks where he raises red and tubifex worms for use in his fishroom. The tanks contain a 1.5 in. layer of fine sand substrate, are equipped with air-driven small corner filters, and contain numerous snails and healthy numbers of daphnia. He feeds spirulina pellets every other day, usually right after harvesting worms and/or daphnia. He harvests worms every other day, collecting from only one side of one tank each time; this way the majority of the cultures are untouched for nearly two weeks at a time. He scoops the sand out with a cup and pours it into a 1 gallon shoe box, then stirs the sand. The worms collect into a loose mass; the sand is returned to the tank.
Blackworms often arrive with accompanying gray-white leeches. If you feed the worms in a semi-wet state from a plastic container, the leeches will often adhere to the plastic. The few that do get into the tanks will do little harm. A Clorox rinse eliminates the rest.
– G.C.K.A. Newsletter, February 1999