Air bubbles on sand??

Hey guys, havin a spot of bother with lots of tiny bubbles on the sand!?
the sand seems to be covered in algae each day, im running phosphate remover and when i test for phosphate it shows zero!!

any advice?
i been turning the sand over and giving it a rake about, should i remove some and add new sand??

 

Algae feed off nitrate. How old is your tank and do you do water changes? Those bubbles are nitrogen produces in the nitrogen cycle. It's good, but you may have high nitrates.

 

The bubbles could also be oxygen from algae, such as cynobacteria, whenever I have a cyno outbreak, you can see tiny little bubbles all over the rocks and sand.

 

I'm thinking this is the case.

In a healthy tank, where the sand bed is sufficiently deep and relatively undisturbed, anoxic regions harbor the bacteria that turn nitrates into harmless nitrogen gas. I've experienced it myself, and under the best circumstances--the bubbles rise right off the sand bed. Maybe a dozen or so every minute.

If you have green (or not green) algae covering your sand, and air bubbles occasionally break from that--this is probably the result of photosynthesis, and is O2, rather than nitrogen.