micro bubbles in the tank

[chi_chi_mpet]

hi

i can use some advice..... i just put together a 55 gal corner reef tank with a 21 gal sump.... i have been having tons of micro bubbles in the tank..... i shut off the pump and the bubbles go away.... so obviously that is the source of the bubbles... so i checked the connections....tightened them with secure clamps.... checked the sump area and the water is without bubbles..... in the pump section.... the pvc tube has a 90 at the top where it connects to a duel out let.... i have changed this a couple of times and done it with a single outlet and back to a double.... no change.... there is a hole in the bottom of the 90.... that the aquarium shop person told me needs to be there and not covered.... so i have to wonder ...... is that causing the micro bubbles and how do i get them to go away.... i cant put it under water since it is in the obverflow area.... so it is always going to be letting air into the line.... i dont know why but they say it is so.....ok ..... i am new and confused... need some help

thanks

[OneDummHikk]

When you say a hole in the bottom of the 90, are you talking about at the end of the return where it goes into the tank? If so, its an anti-siphon hole so that if the power goes off then the water in your tank won't get siphoned into the sump. But, it can be under the water and still work like its supposed to. Simply drill it 1/8-1/4" below your water level. To find out if that is where your bubbles are coming from, turn the return pump on and put your finger over the hole. If you still have bubbles, that isn't it. If it stops the bubbles, you know what the problem is.

Good luck with it and HTH.