If you can start train your fish to eat market prawn then it would be better, but if you're refer to to stick with live feeders then nothing wrong with it (there is no right or wrong using live feeder as stable diet) but you will need to do some extra work if you care for your live stock. You will need 2 small tank (5 or 10 gallons) buy feeders or fish up bluegill and put them in 1 tank have salt, methane blue to treat ick a very common disease, and you might also treat your live feeder for internal parasite (hex/hith), then buff up and gut load your feeders with high quality pellets before give it to your predators so your predator will get enough nutrition and better health for long life. After quarantine the batch of feeders move those to second tank ready to use, and get new batch of feeder and repeat the process. It's a lot of extra works to do and that's why most of us avoid to use live feeder as a stable diet for our predators.