thanks for all your replies to my original question. we tried aphids and the danios loved them. they were all over the heart of some bok choy we had in the garden so we just put the leaves, aphids and all into the tank. they picked them off and some of the fish ate some of the leaves too, i think. also tried green looper caterpillars of varying sizes that were on our tomatoes. no problems there either, all the little fish had a go at them. i also have a bucket outside with mozzie wrigglers, which i catch and feed to the fish, and there are bloodworms growing in there too. does anyone have any idea how long i need to purge those for before feeding to the fish?