Relatively young tank (~6 weeks now) is starting to show algae growth after introducing frags that were somewhat encrusted with green and coralline algae. Nutrients have been extremely stable because of low bioload (no fish) with NO3 around 5 ppm and PO4 between 0.03 and 0.1 (both by Salifert). Just hoping for help ID'ing the brown spots, is it algae? diatoms? dinos? Sand still looks pretty clean, the growth started on the highest pieces of rockwork closest to the light so it's definitely photosynthetic. I'm starting to introduce a few different snails as CUC now.