ok...
that stuff you are seeing is mostly algae, but also some
diatoms and could be some
cyano.. (and many other things)
this stuff is very normal in a
DSB, is nothing to worry about.
now on a side note i would like to make 2 recommendations.
Salinity.. your
SG is a bit low, i would recommend moving that up towards 1.024-1.026 (i maintain 1.026)
Nitrates.. get rid of those bio-balls, and you will likely get the
nitrates stable... Bio-balls are meant for
FO tanks and are NOT recommended for use in a reef tank
