What air bubbles on the water surface mean
If the rising air bubbles from an air stone remain for a long time or even cover the entire water surface, this can be an indication that the water is too heavily polluted with persistent organic compounds.
Like a protein skimmer, the protein compounds in the water make bubbles.
Careful and regular water changes can help. In addition, it must be checked whether the stocking needs to be reduced or the feeding reduced.
However, long-lasting bubbles occasionally form in aquariums that are not heavily biologically loaded.
In some cases, a scum keeps the blisters below the surface.