Considering total system reset...

[tlhood]

I'm sorry to hear about the current string of issues you've been having. I saw your build thread and your tank looks/looked really nice! I am extremely jealous of your cowfish too. I saw a baby one in a LFS a while ago and it was sooo hard not to bring him home.

albeit my tank is smaller and newer than yours, and didn't have too much coral in it when I had cyano so I'm not sure I can compare my cyano issues/remedies to yours... But I was also weary of putting chemicals (even chemiclean) into my tank.

I ended up going the blackout/more flow/less food route. I would suck up as much as I could during a water change, and I blacked out my tank for probably three days (no sunlight or anything). I also made sure my filters and junk in my RODI unit were working properly. After the blackout period I did another change, and I would slowly ramp up the amount of time my lights were on, starting with as short as 4 hours a day. I still spoil my fish with food, but it seems my nutrients are being exported sufficiently now.

I read that some people with really bad cyano outbreaks would do the blackout, then dose the chemiclean while the cyano is down. Others said that tiger conches can eat it too.