No, feeder fish are not okay. They are a huge parasite risk, and some of the species they sell at pet stores have a chemical in them called thiaminase which is bad for most reptiles.

The only time fish are okay is if you feed frozen/thawed silversides (which you can get at most petsmart/petco). Those don't contain thiaminase and have been frozen long enough to kill parasites. You can feed one of those like once every two weeks as a treat.