Micro Bubbles HELP!

[NYfan78]

I have a red sea max 130 model. I have the media basket with the tunze 9002 skimmer. I have modded the return pumps with intake tubes going father down. The return jet closest to the out side wall goes about half way to the bottom where the other tube goes almost to the bottom. I have messed with all different lengths or the intake tubes. I am still getting little bursts of micro bubbles only from the right jet(closest to the middle). All the water levels seem normal. I have taken both pumps out and sealed with with silicon. I need help figuring this issue out! Help!