i put small valves on my airline tubing to adjust how much air goes in , works every time, so instead of restricting the drain itself to make it quiet which is a bad idea if you dont have an emergency you restrict the air , the less air the faster it drains your overflow box(put your finger and block your durso it drains the b ox fast untill air starts to get taken in and make horrible noises) the more air you allow in the slower you make the drain.

also if you change your stockan to a durso much less air problems too.

So I picked up 4 valves to control the air intake from the overflow, and it did help a little. Bit I'm still getting a lot of bubbles.

Any other suggestions for the tank to tank, I'm going to try the T on my sump drains.