Steve I rate this skimmer from 50 gallons to 150 gallons, that is for a medium to heavily stocked tank.
Lewy, I had to reduce the size of the screw from 1/4-20 to 10-24 to make them go in the new location so I felt that small of a screw should be stainless for strength. I still use 1/4-20 nylon bolts on some of my other products, they are plenty strong.
