All mine seemed to go through that around the 7-8" mark. It's almost like a phase, that's when their growth starts to slow down and maybe that has something to do with it. But don't do feeders anyway-not good nutrition and you'll end up introducing ich or some other disease. Oscars benefit from a varied diet (as all fish do). Try to get him to eat veggies if you can and they also go nuts over shrimp, earthworms, bugs and pretty much anything else.
