I don't use feeder except for the odd insect/invertebrate. I guess there's nothing wrong with it if you breed your own but if you have a community setting or fish that aren't really that predatory it seems excessive. . Plus it does breed aggression at least in my experience. I remember I had 4 centrarchus growing in a 29 gallon tank. I added in some small livebearer fry for them to eat. After that it was impossible to introduce new fish into the tank. Anything that tuched the water they would snap at. These were 3-4" fish. And it's not like these were big predatory fish. If you have like a solo jag or oscar than I can see that but feeding feeder fish intentionally to something like a convict seems a bit excessive IMO.