I started both my wild and farmed pbasses out on live fish - guppies and rosy reds when they were smaller. My Pbasses, which are also about 4-5" all eat Hikari pellets right now. There are some really good threads on MFK which go over different ways of getting your pbass to take prepared food. I'm sure you can find it with the search function. It worked for me. So now every time the pellets hit the water - the pbasses hit it like they use to hit the rosy reds. Although for some odd reason, the ones in my tank prefer pellets over market shrimp and chunks of silverside.
