I put the guppies in the 55 and was feeding a couple of them every two days to the oscars. They were all pregnant females and they all gave birth within about a ten day period. I went from having about 20-30 pregnant guppies to about 100 guppies. When they all gave birth the ammonia spiked and i couldnt get it back down or get the guppies out. I got some of them but the babies are hard to catch. And as for feeding, all my pacu will eat is algae wafers or the flakes i put in there for the guppies. He ate grilled cheese once but hes a pretty picky eater.