I have a 10 gallon with an external durso type of overflow. Anyways, when water drops from the overflow to the sump, there is allot of bubbles going to sump. I have a bubble trap built but I guess that its not enough.

Will a filter sock help?

Here is a picture of the overflow.. I can get a better picture though


Also, the black thing is gone, its just a 1/2" drain now.

I have a 4 x 14 felt sock and the multitude of bubbles don't get through it.

I fixed the problem, the drain pipe from main display was too large and allot of air was getting in... I closed the valve half way and now everything works like a charm, no micro bubbles in sump.

Where is your valve and does that lower your flow rate?

I have two valves, 1 for the return and 1 for the overflow. I had the overflow valve full open but then that was the one causing allot of air getting mixed with water.