Where could microbubbles be coming from?

[Clancaster23]

I just switched out my sump and return pump and cut my returns from four to two (I had four total bulkheads in the back of the tank, I plugged up two). I was still getting microbubbles with the old pump but it was dialed back some (MD 2400) and had more plumbing twists and turns to it so I figured that's why I had a bunch of bubbles flooding the tank. Now I moved to this Quiet One 6000 pump. Now I have just two bulkheads it's sending water through but I am still getting a flow of microbubbles coming through both bulkheads. I have the pump running wide open and even have a long round filter sponge over the intake of the pump and I still get the microbubbles. Where else could they be coming from?? The return section of the sump isn't overwhelmed by bubbles, just a little from the other two parts flowing down over the baffles into it and you'd think the sponge over the inlet would take care of those.


I only have one T in the plumbing, that's splitting the water in two straight out from the pump after my gate valve. I then have straight pieces form the T going to 45's and then into nylon reinforced flex hoses up to the bulkheads, then a 90 into the bulkhead. Only thing I can think of is the flew tubing, you can see dark spots in it. I'm guessing it's spots of algae or something and maybe the bubbles are coming off of that? I have no clue. Maybe since the pump is brand new it's still getting slimed up and will eventually stop shooting bubbles out? This really kills the look of a tank.

 

[ca1ore]

If you are getting significant bubbles (rather than just a few) then its usually either bubbles being generated in the sump from a skimmer, drains, etc., the pump is sucking air, or there's cavitation in the pump volute chamber. A pre-filter sponge isn't likely to do much for bubbles, and may actually be restricting the suction side. How high above the suction end of the pump is your normal water level?

 

[Clancaster23]

Right now there is 9" of water in the return section of the sump. I actually have my skimmer discharge pipe in the same skimmer section so that it doesn't flood the return section with bubbles so that isn't the problem. The problem I figure is from the return chamber on up.

 

[Clancaster23]

I swapped the sides of the skimmer and fuge and I still have to turn the pump down about half way to avoid getting a steady flow of bubbles and even then, I get a small amount but not enough to bother me. Now that I see I have to dial it back about half way, this pump puts out 1664 gph max and that's before you add in the head and plumbing. Am I still getting enough flow out of it to run this system efficiently? I have a 40 gallon sump with an ASM G2 skimmer.