bubble build-up

We have about a 2" layer of crushed coral/live sand mix in our 75gal tank. We have been having problems with exccesive bubble build up in this base. All water tests have are good. Our regular 20% water changes have been every 3 - 4 weeks.
WE have the following in our tank:

50 blue legged hermit crabs
3 turbo snails
1 yellow tailed damsel
1 juvenile emperor
1 regal tang
3 ocellaris clowns
3 bubble anemone
green frog spawn
xenia
star polyps
button polyps
1 peppermint shrimp
1 cleaner shrimp
2 egg urchins

The bubbles also collect on the live rock, and sides of tank. Maybe a combination of things or one main culprit. Appreciate any thoughts.

[StirCrazy]

what kinda bubbles are we talking about?

Steve

clear air bubble.

[StirCrazy]

do you have a sump and return set up? or is it a sumpless tank? If you are using a return pump and a sump is it blowing tiny bubbles into the tank? and if it is sumpless do you have a skimmer or filter that is putting some bubbles in there?

Steve

Originally Posted by StirCrazy

do you have a sump and return set up? or is it a sumpless tank? If you are using a return pump and a sump is it blowing tiny bubbles into the tank? and if it is sumpless do you have a skimmer or filter that is putting some bubbles in there?

Steve

I do have a sump and return set up with a seaclone 100 skimmer. I have been watching these items as well as everything else but haven't seen any evidence of them producing any bubbles or micro bubbles. When you look at the water with just the moon lights on there is a few bubbles in the water. The only time/place that we see these bubbles is on our live rock and on the gravel base. We get rid of as much of these water bubbles as we can during the water change stage but they start showing up within a week.
We have been running this tank set up for 9 months and this problems starting showing up a couple of months ago

[danny zubot]

The only times I ever see air bubbles on the sand bed is when a cyano bacteria bloom is about to start or denitrification bubbles. Do you have red slime on the sand bed that trap these bubbles or are they coming from under the sand? Denitrification bubbles are normal in a healty sand bed, but if its a coating bacteria like cyaon, you should look into some form of remedy.