I had the same problem and it drove me nuts.... I spent way too much time adjusting the height of the stand pipe and the amount of air it was drawing. Then I read that the backpressure could be the cause so I cut the pipe into the sump so it was just below the surface and that made all the difference in the world. Then again, I remember another guy having the same problem, but my solution didn't work for him though.
I lose sleep over this type of stuff. I'm still constantly adjusting to try and optimize it. I have it much quieter with no gurgling, but still a ton of bubbles are being produced in the first section of my sump.
I have resorted to bioballs in the first chamber to defuse the bubbles....it works, but I worry about them crashing my system eventually....
LOL.... my intention wasn't to hijack your thread when I started writing
but now I realize I got questions.....sorry.
How long would you let them sit before taking them out to clean them?
How would you go about cleaning the bioballs?
my sump then goes through a fuge and then into its final chamber. Between the fuge and the last chamber, is an over-and-under baffle with a few bioballs and some filter floss. Its purpose is to keep the macros out of the main tank and diffuse remnant microbubbles.
It's not the ideal setup, but it's all I can think of that seems to do the trick. My only worry is the longterm effect of the bioballs, even if they aren't being intentionally used for filtration. Thoughts?