Coryman; blackworms are also known as black mosquitolarvae; they're the larvae of the gnat/mosquito: Culex pipiens. A very good food, recommended, because it often stimulates spawning, and they're most abundant in small volumes of water, where fish don't dwell (such as the rainbarrel). Collected from the rainbarrel, or any old bucket lying in the garden filled with rain; they're VERY SAFE.
I nearly always use frozen food, because it's a lot safer than live; how many times I've found fairly huge leeches in with live bloodworms, white mosquitolarvae or even daphnia's....
not to mention planaria's, hydra's etc etc.
And most waters -even small ones- over here are polluted and packed with fish (for the rod-swinging league) so all the fish-parasites are quite abundant too. That's what happens if you put in 400.000.000 fish every year to satisfy them.....
haven't seen many frogs or newts in years
