Guys, we need to consider that these Pickerel have a minimum size limit of 15 INCHES...... Assuming the fish can reach 15" but likely a fair amount larger w/ 15" as a minimum to legally harvest, I don't see how Stone cats aren't on the menu for them. Esox are highly predatory and swallowing a catfish can be fatal to countless species of animals in general. Let's not forget also, Esox grab their prey SIDEWAYS and mouth it for a bit before flipping it to swallow head-first......if that happens, the 1st thing that will happen to the Pickerel is a dorsal spine through the top of it's mouth, or worse HEAD.
Thoughts?
Also, I have spent 30+ years under the impression stonecats only grow 4-5" and it takes about 10 years for a Bullhead to reach a FOOT.....20" is a loooooong way away.
EDIT - wow, stupid common names....had no idea they could grow 12". The question is "are we talking about Noturus flavus or other Madtoms commonly all referred to as "Stonecat"???"
I missed a few things you said. in the home aquarium Redfin get max 14 but mostly stay between 7-10 inch. while grass picks are in the same ballpark they usually are 2-3 inches longer. lastly the chain pickerel is double the size usually obtaining lengths of 22-30 inch.
Also I've never kept bullhead. I'm a fisher so all my interactions with them are in the wild. So i have no knowledge of their growing habits in the home aquarium.