Rarely do I recommend additives for a tank, but for cyano, nothing beats using erythromycin[FONT=arial, sans-serif]. In both FW and SW, my experience is that after 1 course of treatment, it has never returned. Some argue the use of antibiotics is bad it will come back if the underlying cause is not addressed. In the case of cyano, I have never seen that to be true. [/FONT]