I lost a Blond Naso about 7 inches. But that was my only loss. All other livestock seems fine. Anemones, SPS, LPS, and softies all survived unaffected.
So in Summary:
1). Heater malfunctioned. It had an internal failure that cooked and cracked the plastic covering. Somehow it either leached contaminants like burning plastic into the water. About the only comparison I can think of, would be trapped ins room with burning plastic. Either the burning caused the oxygen to drop or it leached toxins into the tank that caused the fishes' ability to get oxygen from the water. I'm thinking it was the toxins.
I only had two indicators. I noticed the Achilles Tang upside down and breathing hard. The other indicator was a slight burnt plastic smell in the fish room.
2). All parameters were normal and within acceptable levels. Either Sam or I tested salinity, ammonia, nitrate, nitrite, calcium, Alk, Magnesium, PH, temp, and copper. From a testing perspective, I never found a parameter that I could point to that would indicate a problem.
3). This happens quickly and you must act just as quickly. But don't be stupid. Be methodical and logical. For example: I immediately removed the most likely culprit with the minimum disruption to normal tank operation. Try to keep the core systems on line if possible. I firmly believe this helped too.
I suspected the heater because all pumps seemed to be working fine. The heaters shouldn't even have been on. It wasn't hot like it was on, but the increased temps made me suspicious of the heaters (I have 3 installed).
4). Water changes: While more may have been better, I only had just over 20 gallons. That's less than 10 percent. I started the RO/DI for more water changes later. Even a quick small water change is better than nothing.
5). Mechanical filtration. While it's been about two years since I used activated carbon, I still had some on hand. I filled a Phosban 150 with quality carbon. Of course since I was in a hurry, I couldn't get the O-ring to seal. It kept leaking and spilling on the floor. So instead of hanging it in its usual spot outside the tank, I just reversed it so that when it leaked, it leaked into the sump instead of on the floor. I did make sure that it did have adequate flow through the media.
I also threw three bags of carbon/phosphate remover/poly filter combo into the sump also.
6). When things start to turn the corner, stop trying to change stuff. Once I saw the small, low oxygen consuming, fish starting to become active...I knew I was turning a corner towards tank recovery and stabilisation.
The next morning ALL fish appeared normal before the lights were on. On my way to work I was happy because all fish seemed to be alive and well. Unfortunately by the time I got home, the Naso was somewhere in the rock work struggling for his life. I eventually saw where he was hiding. He was breathing heavily. All other fish were fine. The Naso died either last night or this morning. I couldn't locate him for about 12 hours. I eventually saw just his tail sticking out deep in the rock work. I removed him to prevent an ammonia spike and another tank problem.
I changed another 10 gallons of water today because it was already made. I now have 60 gallons of fresh saltwater made and ready to go if I need it.
Bottom line is that if I didn't have carbon and poly filter on hand and failed to act quickly, I would have at least lost all my fish and maybe my corals.
Luck and semi preparedness on my part (and Sam's) saved about 20 fish and several hundred dollars.
Thanks to Sam for being Johnny on the spot with some additional manpower and extra backup equipment/supplies.
Il post pics of the heater shortly.
