Earthworms for fish food

Brine shrimp makes for great fish food and is easy to breed. My friend ran a brine culture running for 2 years on her back step. Hatched some brine (or you could buy some adult brine) stuck them in a bucket on my back porch in discarded tank water (from water changes) and let the sun do its thing. Rain topped it off, sometimes I topped it off, but otherwise it thrived on neglect, froze over in the winter, and came back to life in the spring. No heater, no aerator, no nuthin'. Why bother with worms? --Fishfool @ The Reef Tank

Eisenia foetida secretions can cause problems with fishes gills. I used them with newts, fish, etc. with no apparent problems but have been informed by a reliable source they are somewhat toxic and have killed fish in experiments.

I raise compost worms (setting it up as a side business, actually: http://vermontworms.com/). The "foetida" in Eisenia foetida comes from Latin which means something like "stinking". I'm not sure how toxic it actually is, but I can confirm that fish don't like them much. I've seen sunfish, bass, and perch in aquaria take them greedily, only to repeatedly spit them out again. I think my bullheads responded in the same way, but don't recall.

Other species of worms are probably far better for fish food, but not as easy to raise. You can't put nightcrawlers you'd find here in North America in a traditional worm bin. As burrowing worms, they need to be able to form permanent deep burrows. Eisenia foetida meanwhile are litter worms, and are adapted to living in loose organic material. Eisenia hortensis might be a better choice.