Well I don't care about bubbles in the least and I don't think fish do either. I hear that some coral definitely doesn't like bubbles.
Bubble traps...
Anyway, bubbles float right? Well you can imagine that you could get rid of bubbles in a bunch of water by just drawing from the bottom of the column. This is one hundred percent true, unless, that column of water is moving. In that case the bubbles can be "entrained" and be drug down with the moving water. Well if the column moving down is slow enough the bubble's buoyancy which is moving the bubble upward will win the race. Hence, the bubbles won't make it to the bottom - you have "trapped" them.
To review. If you had some dinky bubble at the bottom of your water column detach and rise to the top it will rise at some speed. Your system needs to maintain flow that is S L O W E R than that. If that is assured then you won't get any bubbles passing thru.
How this translates to a sump design is that you put a plate in the flow path somewhere where the water must go down to exit. You need to make sure that the spacing involved is such that the flow speed remains below the bubble rising speed. Bigger flow? Larger areas are required.