also if you don't have any some snails will work wonders on that algae, Turbo's are big eaters, and you can get some misc snails to clean up whats left behind them... Some crabs are great about eating it aswell, as they can get down into the pores with their claws and eat the roots of the algae....Just keep in mind adding a clean up crew will only patch your problem, not solve why you have algae in the first place...
That RO reading just seems weird to me... what meter are you using, and do you filter the RO yourself or is it store bought?