Tubifex worms (Tubifex tubifex, most likely).Tubifex are oligochaete ("OLL-ago-KEET" meaning "few bristled") annelid worms. The species with the universal distribution is Tubifex tubifex, but in Australia the usual aquarium tubificid is Limnodrilus udekemianus, according to Wormborough Aquarium Plant Nursery in N.S.W. who show you how to keep large quantities of tubifex alive for a long time. More than four dozen Tubifex species have been discovered, some from pretty specialized environments, like the abyssal sediments of Lake Baikal, the mile-deep rift lake in Siberia. When tubificid species in Malaysian rivers, lakes and artificial ponds were compared with a temperate lake (in Poland) only one species (Limnodrilus hoffmeister) turned up in both tropical and temperate waters. In Malaysian waters, the tubificids were far more common than the spottily distributed Naidid worms, which we may also find in our aquaria. And the lumbriculids, like our popular California Blackworms, were absent from Malaya.

Like their distant earthworm cousins, tubifex are hermaphrodites that produce both sperm and eggs in the clitellum, which is that band around the middle. In natural waters, aquatic worms dominate in soft bottom sediments. The richer the water, the greater the population of Tubifex. Tubifex stand on their heads to feed on organics in stagnant lake bottoms, where they build up a protective tube in mud. "Tubifex" means "the tube builder," so don't get side-tracked with even-quite-knowledgeable folks who call them "tubiflex." It's a good error, though: "tubiflex" reminds me of the lax movements of a red rubber garden hose on a warm afternoon.

When you're keeping them, you'll be omitting the mud of course, but don't drown them, as I've done many times. They'll survive better at cool temperatures, to slow their metabolism, and in water so shallow they can reach the surface. I flush them morning and evening, gently, using just enough water force to break up the ball of worms. I've noticed that they survive better if the last rinse is with water that's been passed through charcoal (in a Brita filter). The consensus is, they're stressed by chlorine, but I also suspect copper in my tapwater.

Tubifex fears. Since tubificids can get by in virtually anoxic conditions, their detractors sometimes warn that they ingest anaerobic bacteria, and associate intestinal ailments in fish with feeding tubifex. My own feeling is that anaerobes are likely to predominate in any intestinal fauna and that includes fish intestines, and the clean conditions in which you've been holding the tubifex have largely purged their intestines anyway. If toxic bacteria are killing fish, dead tubifex are more likely culprits than live ones, to my way of thinking.

Tubifex is also sometimes singled out as the alternative host transmitting the sporideans (Myxobolus cerebralis) that cause "Whirling Disease" in the young of some coldwater salmon and trout species in hatcheries. The specific parasite concerned, Myxobolus cerebralis, lodges in young fishes' brains, as its name implies, and disorders the central nervous system, causing spinning and staggering. This is a coldwater parasite that doesn't affect even all species of salmonids, let alone any tropical fish. Though other myxosporidians do infest tropical freshwater fishes, tubificid worms haven't been implicated as their transmitters. Other pathogens besides sporidians are vectors of central nervous disorders in our fishes; they include viruses, bacteria and fungi, none of them treatable by the time symptoms appear.

If you have lingering doubts, read Maria E. Markiw, "Salmonid whirling disease" at the WV US Fish and Wildlife Service website.

Capillaria have been transmitted through tubifex in lab experiments, according to the ZFIN website, but the common method of transmission in aquaria is from fish directly to another fish.

Tubificid worms can also be intermediate hosts for some tapeworms found in wild-caught fishes, I understand. In the aquarium the tapeworms can't complete their complicated life-histories and aren't ordinarily a problem. Dr. Barry Cooper, Dept. of Veterinarian Pathology at Cornell, a major mover at the American Killifish Association, is one who feels that the disease issue can get overblown and can generally be traced to dirty culturing. He avers the innocence of tubifex, according to a post in the thread "Pathogens and Tubifex/Blackworms" at the Live-Foods Mailing List, 13 Dec 1998 (you'll have to search that month's postings to read it). David Robinson's follow-up post, 12 Aug 1999 is also apropos. A June 2001 e-mail from Barry Cooper was posted at AquariaCentral. It read in part:

"Many foods can act as "carriers" of organisms, particularly bacteria. Thus, tubifex or blackworms, particularly if they are not in good condition (i.e. some are dead or dying) could be contaminated. Similarly, many people believe that improperly stored frozen bloodworms can be a source of bacterial infections. Finally, any rich high protein food can result in a heavy burden of excreted wastes in the tank, which could favor bacterial infection.

"I know of no definitive work to prove or disprove a specific role for these worms in disease transmission in aquarium fish, although I do know of some other scientists who do not believe that they act as intermediate hosts for infectious agents. I use blackworms because they are available and are cultured in clean conditions. True tubifex are rarely available these days, although many stores sell blackworms as tubifex. Tubifex, when available, are likely to have been harvested from dirty environments."

This should be reassuring, on the whole. I tend to think the prejudice against tubifex worms may often be connected with these low-life origins, near sewer outlets, as their detractors never fail to point out. Or in the effluent from breweries and distilleries, as Dr. Gunther Sterba noticed. Low and boozy, either way, sort of a "Liza Doolittle Syndrome." In southern California you'll hear that tubifex are brought in from Mexican sewers: a detail, I feel, that speaks as much to Californian prejudice about Mexico as it does to any tubificid reality. Are collectors of wild tubifex still slogging in hip waders through sewage mud to supply your LFS? Even so, after a day or so in clean water, flushed with de-chlorinated tapwater and with their digestive tracts empty or fed with squeezings from your sponge filter--— I think, Pickering, that Eliza Tubifex is ready for the Embassy Ball.

As a general rule, the better place to look for pathogenic strains of bacteria is in or on sick fish, rather than in or on invertebrates.

Nevertheless, this is not what you'll hear from many authorities who write for hobby magazines or post on the web. Many thoughtful, well-informed fishkeepers have repeatedly gone through episodes of mysterious disease that they have associated with feeding tubifex and which have cleared up when tubifex was eliminated from the program. The evidence is always circumstantial. Discus pro Jim E. Quarles, for one, is convinced that tubifex harbor tapeworm eggs that can be passed to your fish. I'm not convinced of this, myself; you'd better read his article "Understanding tapeworms in fish." archived now at the Indodiscus website.

A more urgent concern to my mind, though I never hear it discussed, is the possible problem of "bio-magnification" in any wild-collected bottom-feeders like tubifex. They ingest heavy metals, such as cadmium, and store them in body tissue. A predator farther up the food web, such as your fish, concentrates any toxic metals in its tissues and pays the consequences. In a classic example of bio-magnification in the 1960s, DDT from fishes was concentrated in the tissues of fish-eating eagles, which were decimated. Current bio-magnification issues, which deter us from eating Hudson River fish, are centered on PCBs. So, though tubifex don't transmit parasites of tropical fish, I wouldn't feed wild-caught tubifex after all, because of this bio-magnification issue.

Culture? Most folks buy tubifex at the LFS, but Dan Carson cultures them in a tray with garden-store cinders, fed with fish-meal based pelleted fertilizer. Cultured tubifex avoid the biomagnification issues, and they must avoid any lingering possibility of transmitting parasites. Dan Carson's 1997 directions for culturing tubifex are archived at JAWS: www.actwin.com