I realized in my ten gal tank that there were these weird green things coming from the rocks. It comes of easily and when I tried to take it out of the water, it flaked off! I am sure this is not their food. BTW, my betta seems stressed out because of this and 2 tetras died. at first, I thought it was alge and told myself to get a scraper. as it flaked off though, I got worried. Can someone please help me? Thanks!