The main disadvantage of using live fish as food is the risk of introducing parasites and bacteria into the aquarium. The cheapfish likely to be used as feeders have, almost by definition, beenraised intensively, and
that means they will have been exposed to allkinds of disease-causing organisms.
Whitespot and velvet are extremelyeasily transmitted between feeder fish kept in cramped quarters, andover the long term, feederfish can expose predatory fish to skin and Gill lice, parasitic intestinal worms, neon tetra disease, and a wholehost of opportunistic parasites, bacteria, and viruses.
Goldfish are especially popular as feeder fish, beingcheap and relatively large, but they are actually among the worst of all prey species for most predatory fish. They are fatty and rich in a chemical called thiaminase, an enzyme that destroys the essential nutrient thiamine (also known as vitamin B1). Rosy redminnows, a popular alternative to goldfish, also contain a lot of fatand thiaminase.
In the wild, because fish eat a variety of species, any shortcomings with one prey item will be counterbalanced by the next; so while a gar or channel catfish might catch a minnow oneday, its next meal might be small perch, carps, or killifish.
But in the aquarium, where only one or two species of prey are used, there is a very real risk of vitamin deficiency
By contrast, aquarists taking the time to train their predators to take a selection of frozen
food, supplemented with pellets or flake can guarantee that their fish willreceive a varied diet that will keep their fish healthy throughout itslifetime.