I built this air stone manifold to get rid of all of the little airline tees in a multi airstone skimmer.

I took a 1" PVC coupling and glued a 1" PVC plug in one end and a 1" slip x 1/2" FNPT bushing in the other end.

I drilled four 11/32" holes around the bottom edge of the coupling and tapped them with an 1/8" MNPT tap.

I screwed four 1/8" MNPT x hose barb elbows in these holes and a 1/2" MNPT x 3/16 hose barb in the top.

Install your airstones with short pieces of airline and you are ready to go.

I got the hose barb fittings, tap and drill from www.aquaticeco.com