Google cyclopeeze; their web site will give you more info than you'll ever use. I really like this stuff, most fish love it and there is something in it that sets off a lot of feeding activity in any tank I've used it. Its great for getting picky new fish to eat. IMO, I'd never toss a frozen chunk of anything into a tank. I think food should be reasonably close to tank temp, which is also the fish's body temp.