If its spreading over the LS it isn't "cool" its cyano. :scared:
(1) siphon it out
(2) decrease the amount of time your lights are on
(3) cut back on the amount/frequency you are feeding
(4) increase circulation, cyano prospers in areas of low circulation so make sure you have
at least 10x circulation (10 x gals) going, if not add powerheads; if its just in one area
adjust your PHs or add another one for that area
Good Luck