Backyard Aquaponics
A place to discuss aquaponics

We have a small 40g tank with about 7 small bluegill. 5 are about 1" and 2 are about 2".

We're feeding them natural foods and one of the main things we feed are blackworms, that tend to clump up. One of the bigger fish in it steals the food, takes it to the back of the tank and will fight off any other fish that tries to eat it.

Is there anything we can do to fix this? We can spread out the food more but he's still picking on the other fish.

get some pellet food, (high protein, over 40% at least)
while live food good, it should be viewed as a supplement to a good quality food, which will provide most of the nutrients that your fish and plants need

The small ones will get a chance to grow once the big ones are big enough for you to eat. Uneven growth is normal and just the way nature works. +1 for pellets.

We can't feed them pellets. This is part of a research project studying live feed vs pellets. (And the kids would disagree that pellets are a better food. ) The little ones are getting daphnia, mosquito larvae and some of the blackworms, all things they would eat in the wild, so they aren't starving. We're just worried about the aggressive behavior overall.

The pellet tank is the control tank and it's down to only one fish as it is, one of the biggest that was in there. Is it possible he bullied the others? We didn't see any cause of death, water parameters were great, we added salt, we just assumed it was overall stress of being moved or something bacterial/viral we couldn't see.

Maybe these tanks are just too small to keep bluegill, even at such small sizes? They do appear to be a bit aggressive as a species.