so you dont have an ro/di? did you by any chance use tap water in your tank? even once?
also, how old is this tank? reason i ask, is b/c every time i have moved my tank, or set up a new one, even with established water....i ALWAYS get some sort of algae bloom that lasts for several months. i call it the new tank "funk".
i've tried phosphate media in a canister filter during a new tank "funk", and it never helped one bit. which leads me to beleive there is a chemical with a binded phosphate (i.e. not detectable by a test kit, which only tests for free phosphates) either in the silicone, or on a thin film on the glass, eggcrate, and/or PVC or other plastics.
also, what type of lighting do you have, and what size tank?