My Koralia looks like Fabio

use an overnight or longer soak in pure vinegar... then scrub with a good brush or cleaning pad... I use a blue cleaning pad that I got from petco for $3 to get the stuff off. I use it on everything in my tank, and only rinse it clean with tap water, so it never gets contaminated. You'll have to scrub it as I've found that a soak alone will not get it all... when you put it back in the tank, just hope that coralline will cover it before hair algae does...