I have had my tank for 4 months and I am getting worried about the brown covering on my sand, rocks and corals. Can anyone point me in the right direction, I've heard of people doing blackouts for a couple of days but I'm not sure how my corals will fair. I have a fluval evo, ai prime on toned down Saxby settings, filter basket in chamber 1 with floss and fritz. Chamber 2 has the sponge which I've cut the centre out and filled with bio balls. I also have an ai neuro 3 set to 30%.