Sounds like you don't want the catfish. You should remove every one you possibly can. They are competing with your bass. I wish I had never stocked them in my pond. They are hard to catch even though I enjoy eating them. The small bass need to be removed as well. If you are after large bass I'd leave the bluegill alone. If on the other hand you are after large bluegill, you'll need to remove some of them as well. I'm sure some of the real pond pros will let you know what will work. Feeders can be helpful without breaking the bank. Check out some of the units available.

As far as the filamentous algae. It seems to be a never ending battle to keep it under control. Not sure of Missouri's laws but you could possibly get permission to add the tilapia. Good luck and Keep us updated.