Large bubbles from drain

[reefpeeper]

I recently cleaned my return pump and now every now and then large bubbles come out of my drain tube in sump. The tubes output is under the water surface. This never happened before, but im assuming it is doing it because the pump has more flow now that it is cleaned. Also my return is a dorso standpipe. Any ideas what i can do to stop this? Do i have to make hole bigger in cap on standpipe?

 

[reefpeeper]

Anybody

 

[Jimbo662]

How far below the waterline is the drain pipe?

 

[Dorkymk3]

Your drain pipe is pulling in too much air. Might need adjust the air hole