I had a problem with microbubbles coming in through one of my pipes I use to divert water direct to the return pump thereby reducing flow through the sump, I managed to solve it by plumbing the pipe to come down into the sump then make a 90 degree turn at the desired water level, this gets the bubbles to the surface much quicker.. Sometimes a plumbing solution is better than a sponge.. Alan, I have read that a sponge on a skimmer outlet is a bad idea unless you rinse almost daily is this true or just an exaggeration?.
Cooilo
Muz