whatever the source is. put a downturned elbow at the inlet, silicone the pipe seams ect. if theres no air on the way in there wont be on the way out.
The sources are:
1) 35 gal fuge
2] 30 gal breeder
Both of these tanks are drilled with homemade overflow boxes. I've tried the down turned elbow, but the water in the overflow builds up and then surges
Can you give us more info on the drain setup on the other tanks? THey should be totally submerged
The drill holes are about 4 inches down from the top with a bulkhead and screen.
Are the returns that drain INTO the display completely submerged? If so, try bringing them about halfway out of the water, and maybe even add on a bubble trap if there's room- physically and asthetically
There is room over and behind the tank do you know of any examples?