Get your water tested first. Specifically ask for a phosphate and nitrate test. Don't spend the money on GFO
until you confirm your phosphate level. Do you run activated carbon in your filter? What kind of food do you feed?
BTW: that daylight coming in all day is going to be a major contributor.
Also. BRS doesn't make GFO
. They import it from the sole manufacturer for the aquarium industry (possibly the sole manufacturer w/ the patent I think) in Germany. Sometime ago I posted the company who had just been sold to a bigger conglomerate.