i agree with me-n-my-fish in that you need to stop it at the source. Use the chemi-clean now, but only as a cosmetic combatant, and then for the time being try to discover the source of the excess organics. a big one is aerosols. if you wear cologne or perfume, or spray aerosol deodorant near the tank it will act as a source of phosphates, which your tank will absorb, and the cyano will feed off of. Also ake sure you only rinse you hands before working in the tank and dont use soap, because soap also contains phosohates and if they arent thoroughly removed before you stick your hands in the water you can be leeching this stuff into your tank, and the cyano feeds off of it!
good luck
jon