The other problem with fw fish I found was that long term feeding of such, be it fw cichlids or sw fish can cause hole in the head. So not the best choice. Don't ask me why this happens, I have no idea. What I know is from personal experience only. When I raised Oscar, and fed them live fw fish they always ended up with Hole in the head. With sw fish that I have seen others feed fw live fish, I've also seen that they too got Hole in the head.
I also believe that all frozen, freeze dried, pellets, flakes should be soaked in vitamins, selcon & garlic.