Overflow Issues

[sirreal63]

High flow with an open air drain works better with a larger sump, that 20 high doesn't give much room for bubble dissipation before the return picks them back up and send them to the display.

 

[Av8bluewater]

Durso pipe is too high. Simple as that. That overflow box looks really tight on space but I guess nothing wrong with that. That plumbing should not be glued in. Should be threaded at the bottom and slip ons up top that you just wiggle tight. If you lower it it will probably get a better siphon. Probably getting air in it that high up.

 

[Av8bluewater]

If he did it right try to wiggle the top parts loose.. to see if they come off.
If they come off easy get a slip to slip coupling for about $.73 at Home Depot and shorten the pipe a couple inches.