Air bubbles on rocks?

OK I know this isn't bubble algae. I have a bunch of air bubbles accumulating on my rock. I don't have any idea where this could be coming from as I don't have any bubble making thingies in the tank and I don't see bubbles swirling around from the powerheads or skimmer. Any input would be appreciated.

 

How is the water returned to the tank? Do you have a sump?

 

hob skimmers can cause that.also there could be some kind of gas exchange occuring in the rocks.if its just air though you need to find out whats causing it and fix it cause air bubbles can help hair algae to grow.

 

I don't have a sump so there is no air bubble from that. I haven't had this problem before with the hob. I have been starting to get an increase in cyano and I attribute it directly to the bubbles accumulating on the rock. Could it be when I put the powerhead in to decrease surface tension and get some more flow that it is allowing for more gases to stay in the water? Nitrates, nitrites and ammonia all test 0. Waiting to get the phosphate check but not a suspect as I use ro/di h2o. Lights are on 8hrs/day (mh) and only feed everyother day.

 

How is your alk, calcium and magnesium?

 

Where are the bubbles on the rock - top side or bottom? Could be your getting nitrogen bubbles from break down of nitrates.

 

Could be co2.

 

My HOB did this every once and awhile until I put it in the sump. My guess is the HOB. However, I did get this one other time and it turned into red slim.

 

Problem solved. Sand bed was either too deep or not deep enough at 3in. Took off 1-1.5 in or so slowly (over couple of days) and no am not getting the bubbles anymore. My lfs said either 1-2 in or 6-8 anything in between and you are asking for trouble. Hope this helps someone else.

 

Interesting because I'm 3-4in with no problems.