I am currently running a couple of dirt tanks with sand as cap, both tanks are running good but i have a couple of conserns i am thinking of regarding sand vs gravel cap.
In both my tanks there is a build up of gas pockets under the sand, these gas pockets get farly big beafore they have the power to get up trough the sand cap. And when the gasses pull through the sand there always are big bubbles rising trough the water column. This is not a big problem, but my question is how is this when using gravel as cap. Is the gasses only then rising through the water column in small bubbles? Is the gasses getting through the gravel cap in a earlier stage? And is there any benefits using gravel instead of sand when it comes to gas build up under the cap?
I also have some cyano bacteria on the sand in one of the tanks, i guess there is easier for the cyano bacteria to grow on sand beacuse gravel would let the waste sink down in the substrate.