I'm with JokerGirl. I just installed a phosphate reactor on my sump because I was having trouble with cyano in my tank and fuge. I think the homemade fish food I made out of fresh seafood from the Japanese grocery store near me may have been preserved with phosphates, which then kick started my cyano problem. (i use 0 TDS RO/DI water) My cyano is slowly receding. It's great!
One thing to note is, if you buy a reactor, don't put the full amount of GFO (granulated feric oxide) in the reactor to start out. instead, put 1/2 the recommended dose of media in the reactor, so as not to shock your system. gradually work up to the full dosage over week or three.