Microbubbles! But not from skimmer!

I have a microbubble problem, new tank. I thought it might be the protein skimmer like most... But I turn it off and I still get the microbubbles.
90 gallon tank with corner overflow.
I have a 20 gallon sump with baffles and all.
Any suggestions would be great, really starting to bug me.
Thanks Reefers!

 

check your return line....a snail managed to make it upstream in mine and caused a lot of microbubbles....im not sure how it was the cause but i know once i removed him from it the bubbles stopped...i could see him since it was clear vinyl tubing

 

Thanks looked and it's all clear... Tank is only 1 week old.
Thanks for suggestion.
Anyone else?

 

Such a let down after spending 2 months building sump and tank stand. Tanks looks beautiful except for the ugly bubbles polluting water. Anyone that has had this problem before with it not being the skimmer as the cause please throw out how u fixed it.
Thanks

 

is the return elevated above the waterline in the DT? and are you positive its bubbles and not sand being kicked around?

 

I do have fine sand and it does have some residue and sand still in sump from my setup a week ago... It looks like I can see some sand but also bubbles not a lot of bubbles but noticeable. My return pump in sump is under 3 inches of water.
??????

 

Return is elevated above waterline!!! Could that be it!?????!?

 

yes that could be it, try lowering it down a little closer and see if there is some improvement but also you may want to check to make sure its bubbles and not sand....you do that by turning off all lights in tank and in the room and shine a flashlight into the tank....if there is shimmering specks its probably bubbles otherwise probably sand particles

 

I will check both now and get back in a few min.

 

sounds good