It's Bloodworm Season!
by Susan Stacey
This time of year you will see little red squiggles on the inside and bottom of outdoor containers of water. Enough of them make a sort of mosaic on the container bottom. Those are midge larva (blood worms) encased in mud or detritus. Blood worms are not worms at all, but the larvae of tiny flies called Chironomous midges. Once they emerge from their mud cases, these deep red, jointed worms, wriggle awkwardly through the water. They head for the surface and many times attach themselves to the sides of the container. They then sit waving back and forth like strings in the wind and feed. During late Spring and early Summer, you can grow them in any container of still water. They can tolerate poor water conditions.
Blood worms are high quality food that occur in freshwaters everywhere and according to Dr. William Innes, are the most important of all freshwater live foods for North American fishes. Wild fish eat them ravenously and they are a good food for all except the smaller varieties of Killifish. They have a somewhat hard shell, but are an excellent food for mature fishes. They are not to be trusted in a tank with small fry as they are capable of catching and killing them.
You can feed as many as you like but the midge are known to feed on aquarium plants and can do quite a bit of damage if they are not eaten. Also, life of the larva is 7 to 9 days. So keeping them from emerging from the water will take quite a work of nature after a week and a half. Once they pupate, they emerge into a little green fly with large and furry antennae.
One note of caution from Innes. In his book Exotic Aquarium Fishes he notes that instances have been reported of their eating their way out of fishes that had not chewed them ...yikes.