Sump: over/under/over? or the other way?

[kien]

Originally Posted by MikeInToronto

There are still micro-bubbles and it seems these are still there even when nothing is running but the VorTech in the tank. I can't figure out where they come from but it doesn't matter. They don't really bug me and there aren't many. One day I may find the cause.

How high up is your Vortech? What I noticed a little while back is that if my powerhead is a tad too high that it will occassionally cause a vortex and slurp some air into the powerheads intake. The powerheads then dices the bubble and generate microbubbles. It happens so fast that unless you are standing there for a long long time watching and waiting for it you won't notice it.