So I have had my reef tank up and running for around a year and a half now. About a month ago I was doing a water change and was stirring up the sand. After I stirred some of it up I noticed the next day that some of this brown algae started forming. I figured that it was cyanobacteria, although I have had cyano before and it started on my rocks and went away after one treatment of Chemi-clean. So I dosed chemo-clean which put my skimmer out of action because it would overflow even when all the way open. After doing the 20% water change 48 hours later I noticed that more of this algae started forming on other parts of my sand bed. I dosed again and did another water change with no results (my local LFS store kept telling me that it was cyano but I remain unconvinced). After doing some research the best that I could come up with was dinoflagellates. I did a 72 hour black out that knocked out the majority of it, except one little patch, but ended up killing my 2 sps frags. Now a week after the blackout the algae has already come back on my sandbed and I have no idea what to do.
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