I recently built my new Dual 1 1/2 overflow at 900GPH and made a strainer for the top. With the strainer I made it had large enough slots that I was loosing my food down my overflow. So I had two choices of either shutting of the overflow when I fed the fish or come up with a fix. Some times I don't have time to wait untill they eat so I can turn the overflow back on and I have a self feeder I use if I have to leave town. Anyway this is my fix for a food guard on my overflow.
[YT]o0KhYkdJht4[/YT]
[YT]o0KhYkdJht4[/YT]