1st: Corns are mice (and in some cases anole) eaters. Mice provide a balanced and complete nutrition. Fish definately don't. Even for Garters, a pure fish diet is insufficient. I actually doubt a corn would even take the fish under normal circumstances.
2nd: Never feed Goldfish. Even to fish-eating species. Goldfish are considered to be pretty much wholely UN-nutritious.
3rd: And here I'm gonna preach a little. From the statement "I think it was the most entertaining way to feed a snake.", you sound like a potential Live feeder. Please, if you have any actual care for your animals, read up on why live feeding is a bad idea before you do.