I also posted, inquiring about electricity, because that's at first what I thought wiped out the tank (lateral line disease).
Then I posted, inquiring about testing water for poisen.
90 corner overflow, 30 gallon wet/dry sump, BakPak skimmer, 9wtUV, + 350 Boi-Wheel filter.
Ammonia = between .25PPM and zero
pH = 8.2
Nitrate = 80 (yes, a little high)
Nitrite = zero
Copper = Zero
Ammonia = zero
Temp = 75.0 f
Four stage R/O filter in garage. I replace 8 gallons per week. Tank established in 2007, added a few, lost a few. Lost Snowflake Eel on 11-14, Hawaiin puffer 12-6, then everythink else (5 fish) between 12-21 and 12-28.
I dropped water level to 8 inches and kept water movement and did carbon filtration for two weeks, changing it every two days. I moved some sand and live rock into the 20 gal sump under my 125 on 1-11 and lost 5 fish on 1-12, and 2 on 1-13. Since then I have been changing 10 to 12 gallons per day and lost two fish yesterday.
There are two left and the Clownfish is breathing hard. The starfish, urchen, soft corals and YB Gobi look good for now. I am devistated and can use advise.