Blackworm fears. Nevertheless, blackworms are very often confused with tubificids (Tubifex and its allied species) and scorned with equal disgust by many well-informed fishkeepers. You may be told that blackworms "transmit diseases" or, with a precision that sounds even more authoritative, that they "carry an intermediate stage in a tapeworm life-cycle," a possibility with wild-caught tubificid worms. Biologists who know blackworms told me, when I asked, that the response to that tale is "No." Joe Gargas (at the killie-talk mailing-list) sent some to a lab for examination and received a report that blackworms do carry their own characteristic co-evolved parasitic nematodes, as all multicellular animals do, but these can't be passed on to fish. Still, blackworms are dissed as "stinky" and suspect, even at that bastion of good fish information
www.thekrib.com (click to "Foods"), though Randy Carey gives them a better review at "Randy's Fishroom" (
www.characin.com). (click to "Reviews"). I'm with Randy on this. Randy does mention that he inadvertently froze blackworms once, in a metal container in his fish fridge. He thawed them out, and immediately fed them to a number of fishes: still, almost all the fishes died over the next few days. Moral: blackworms must be alive.
It seems the troubles with blackworms themselves come from mass die-off in anaerobic conditions and from feeding dead blackworms. Blackworms do best in darkness, and their metabolism slows if you keep them cool. Blackworms need access to air to be alive when you feed them to fishes. Keep them in a cool room in a wide white ceramic dish in enough water just to keep them covered. Lots of available water surface provides lots of oxygen. I have unhappily drowned them in warm weather in water that was too deep. Every morning, I pour the worms off into a jug and flush them, not too roughly, with tapwater. I let the water gently break up any dense balls of blackworms each time. The temporary pulse of chlorine is okay for blackworms, bad for surficial bacteria. Good worms sink. Dead blackworms turn white. Bad ones, if there are any, float, and I pour off the white floaters, as well as some worms too flaccid to get a grip on their fellows. Then I scrub out their dish. No soap, no bleach, I just scrub it. Finally I barely cover them with chlorine-free water dipped from a plant nursery. If you have some low levels of copper in your tapwater, blackworms may do better in water that's passed through a Brita-type activated carbon filter.
