Please don't take this the wrong way, but it looks like there is some diatom build up on those rocks, the issue may be from water quality as well.
i had the same issue for the first nine months or so of my tank which left me with some very unhappy nems. phosban as well as purigen worked wonders for me. as well as a VERY good clean up crew.
best of luck
i had the same issue for the first nine months or so of my tank which left me with some very unhappy nems. phosban as well as purigen worked wonders for me. as well as a VERY good clean up crew.
best of luck

