i had the same issue with my tank. I thought it was coraline until it grew on my sand bed. I cut back on my lightning, stopped feeding so much and inceased flow! This corrected the issue. Also, as said, this is just part of a new tank. My lights are on more hours a day than before my break out, i fed a lot more, but the flow is still there. I still get a slight case of it, but its just under the arch in my tank where flow dont hit. If you are going to test for phosphates, make sure you test the water that you are using for water changes. The cyanowill suck it up so it will test lower than what it really is.
Also, have you tried just taking the damsels back to the LFS for a few bucks? Or, I am sure someone out there has a big tank that will take them from you.