I'm not a hydro-guy, and not familiar with your setup ... but, the only thing I know of that kills algae, is chlorine bleach ... I would say to dump all your water out, wash down the tanks and tubings, etc., with a watered-down bleach solution ... then rinse it out, and replace with your water/nutes mixture ... you evidently have light getting to your tank, etc. for algae to grow ... no sunlight allowed in the water reservoir ... that RO machine probably needs its filters changed, and the solids are more than likely to be calcium buildup, (which usually acidifies your water) ... hope this helps a little :smokin: