I have had a lot of luck useing it in minnow traps but I don't feed it to my fish, to messy and fatty. I use to feed the sunfish at a pond near here, they loved catfood.
I have used dry dog food on small fish that grow fast and need to be bulked up like catfish for example. It's good fishing bait too. I'd throw hand fulls in the water to float at the surface. It would attract Carp and catfish. I'd super glue hooks to pieces of the food and cast it out there with out a weight when the fish would start feeding.
Anyway...I'm off topic here...
A better option is purina's trout chow or equivelent. It's made specifically for fish and is pretty cheep compaired to foods like Hikari or similar. I use to get the 50 pound bag from a feed store. THey had to special order it in for me but didn't seem to mind. I went thru a bag about evey 4-6 weeks or so. Kind-of messy but worked well. I wouldn't use it on fish I was trying to get good color out of though. It didn't seem to enhance pigment like in red devils for example. I allways used doromin from Tetra to enhance red's orange or yellows. Hikari is pretty good too...