Be sure to have a good light in your sump for the macro. PC works, other types work well too.

Also, I hate to be the guy to recommend a product - the other folks are right in addressing the root cause. This product is JUST in case you've waited long enough to risk the cyano overgrowing any of your corals. For an emergency in the past I've used "Red Slime Control" by Blue Line to complete success with no impact to my fish, corals, inverts. I have softies and fish and am now preparing to get into sps, so I don't know how it'd affect hard corals. Aquadome sells it.