ugh, well I hated to have to do it but I didn't have much of a choice. Cyano got so unbelievably out of control I dosed the tank with chemi-clean on Friday.
Dosing a harsh chemical when things were already so out of whack was not something I wanted to do, but I was siphoning was seemed like a pound of the stuff off my corals and rocks every night, and by noon the next day it would be back plus more.
I have a few corals that got severely damaged that I'm desperately trying to save by cutting away dead skeleton back to just below living tissue. It seems like it's working as anywhere I've cut (if I was able to actually get to where there was healthy tissue), corals are healing over with new tissue and teeny tiny new polyps are forming, and anywhere that exposed skeleton remained cyano free corals have built up new tissue growth edges and the dead spots are shrinking. However, about half of them are so damaged it's not possible to cut all the dead skeleton away as the pattern of necrosis looks like what you'd get if you raked the branch down the fine side of a cheese grater. Cyano got to the point where it was blanketing nearly all places where the skeletons became exposed, and I've found clear evidence that the cyano actually kills coral tissue it remains in contact with for too long. I've got one frag of millepora that never got damaged in the first wave of STN/RTN, but it's small and the rock it's on got carpeted in cyano. About 3mm of it's plate died in a ring around where it met the slime. I have another nearly dinner plate sized colony that had the cheese grater look to it, and cyano formed a continuous mat across the mid-section of the coral. Anywhere that was beneath the cyano is now bare skeleton, even though that coral seems to have stopped losing tissue days before the cyano took hold. I'll probably have to cut the entire thing in half.
So it was a choice between doing nothing and risking the cyano possibly preventing recovery of my corals/killing more than what was already damaged, or dosing with a harsh chemical and hoping I can take back control of the trajectory the tank is on.
Moral of the story kids - don't get lazy and think that just because something has worked great for years in spite of any neglect or ill considered decisions you might have made does not mean that will continue to be the case.
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