Hi

I have these in a 55 gal. planted tank. They are quite small, round and
flat and very hard. I notice them when the lights go on mostly near the top
of the tank on the glass as well as on plant leaves at the surface.Once the
lights go on they start falling to the gravel. Anyone know what they are and
how to eliminate them. They don't seem to bother the plants but they are
unsightly.

Joe