In the pic I posted earlier there is sum algae on that one rock does anyone know what kind it is and what to do about it? That is the only rock n the whole dt that has it and it just at the top of it. I want to stop it before it spreads. My phosphate is .22 with the Hanna and I know what raised it and that problem won't happen again. Not for sure how to battle it so suggestions will be appreciated.