yes that is coraline in the overflow and it does seem to grow there more. but i have noticed the spots coming in on the back glass a bit more. im sure my lights have some effect on it right now but before i changed from my pc's i had even less than i do now. whats in the overflow has grown since the change. i think its my ca levels because i've had problems keeping my reactor dialed in. it has a needle valve for the effluent to run out through and you connect a peice of ro tubing to it and adjust for a drip, well when i get my drip adjusted and walk away, it stops on me, and i have to open the valve a bit more to get the drip back. then it'll eventually stop again, its almost a daily thing. anyone know if theres any other type of valve to replace that thing with?