After the ich outbreak I did vaccume the top 1" of sand(its only 2" thick all over), and since then added another 1" or so on top of it.
Did your problems occur like mine where it would reoccur every few months? I have no problem removing all the sand and cleaning it, but it just doesnt seem to fit in my mind.
There is a thread here that i have not read but puts a "light on in my head".
It refers to pond foam in aquariums,- like how many tanks still running foam for more than 2 yrs????
Perhaps it could shed some information, maybe, I don't know, but I would look for it and read it.
I think since you lost most fish, your system might be starving due to reduced feeding, especially lps that need more nutrients. SPS will loose color and cyano is known to develop in systems with vodka dozing where nitrates dropped too fast.
I've been chasing similar problems for 6-8 months. I suspected everything from baterial diseases to contaminated water. In the end it was as simple as my salinity was too high. My refractometer had drifted out of calibration and along with it went my salinity. A good friend checked with his meter and my SG was 1.035. I'm not saying this is your problem but it's something to look into.
did you test for copper?
no copper has ever or will ever be anywhere near this tank.
Well thats what I was thinking, and why I made another thread specifically asking who had pond foam in their tank for more then 2 years.
From what Ive read there so far and the fact that the foam is not actually breaking down at all, I dont think that is the case. The whole reason I went with that pond foam was because of how many people I saw using it(both coated and not) who were having great results even years after.
Again, Im open to anything but I have yet to hear of one person with a similar problem to mine who has the black foam.
Isocyanate: http://en.wikipedia.org/wiki/Isocyanate
---This foam has a lot of environmental cautions when it's being installed. One thing that occurs to me very strongly is that what is safe in pond (fresh) water is not necessarily safe in salt water, which aggressively dissolves things. For instance: salt water does not readily dissolve calcium carbonate: freshwater does, which is why you dissolve kalk in freshwater before adding it to your tank; BUT freshwater does not readily dissolve copper; saltwater definitely does. What is made for one type of water does not necessarily work safely in the other.
I know that's not good news, but I think it's one really strong possibility. Over time, whatever dissolves out is going to concentrate via evaporation. If this should be the case, the only remedy short of a re-do I can think of is a succession of massive water changes. 40%, then 30%, 30% a few days apart. Try this scenario: The ich was in your tank to start with, got in somehow, but never succeeded well, until an increasingly bad chemical situation lowered natural body slime, and then everything became vulnerable to the parasite. Your corals, meanwhile, were also losing their protective slime, and were increasingly light sensitive, hence the browning, and eventual rtn.
WHen faced with a really bizarre problem, I tend to ask myself "What's unusual here?" and what's unusual is the use of this foam in hot (relative to freshwater) water (a factor in chemical breakdown), under intense coral lighting, light being another factor that can cause many materials to break down, under salt water (another breakdown factor). That is what blinks 'warning' when I analyze the setup and the 'negative' on more common causes.