SMB need more than just FH as they get bigger. To much energetic drain chasing FH. Snacks yes but meals no. Add some GShiners. They will help reduce BG eggs/fry but also FH eggs/fry.

If BG are the problem keep #s reduced by any means possible. YP will eat BG in cold mths well but they will also eat yoy SMB and FH.

I don't care for gate valves as they tend to stick shut and cause major problems unless you open and close them several times a year.