If it blows off with a blast of water its most likely cyano. If so syphon it out as it appears, lots of flow helps. Whats your no3 and po4 at? It is very normal for a new tank to have ugly algae and bacterial stages. In fact if you dont experience this with a new tank you may have worse issues down the road. Just keep up on removing any cyano and algae that appears, keep water quality in check and it will go away in time. As a reef matures and corals grow you will experience less and less algae issues. If you started the tank will all dry rock I highly recommend seeding the system with good bacteria strains like Microbacter7, Seed, Fritz products and Live Rock Enhance along with some small pieces of quality real reef/ocean live rock.