[thefatman]

yup. that's what mine did at first. check the following.

is the pump COMPLETELY submerged in the sump?
are all your hoses tight.
are any/all pvc connection sealed well.
is there a skimmer in the sump?
if so, does it empty near the return pump?

for me it was the last, i had the skimmer discharge too close to the return, so the return was pumping all the fine bubbles into the tank. once that was resolved, then it did the same again after a few days, turns out, as water was evaporating from the sump, the pump exit was out of the water, and it was sucking in air. i turned the pump on its side, and solved the problem.

 

[thefatman]

sounds like you need to throttle back the return pump, or put a bigger drain line on the overflow.

what size drain line is currently on it? internal or external overflow? what return pump?

the pump is pumping more/faster because it is now pumping pure water instead of water AND air..

mine was the same way, when i upped my drain line to 1 1/4" it fixed the matchup. otherwise, you could overflow the tank.