Thankyou all who helped last night (update)

[magdala]

I did a 15 gallon water change with distilled water, I didnt have the salt to add but it only dropped the salinity to 1.022.
I added carbon as was suggested by someone and added in more polyfilter to the fluval.
I was asked if there were any sea cukes or nudis in the tank, and no there was not. I wondered if the foxface dying could have made things worse than they already were...'
I lost about 15 big snails and one torch and it looks like the xenia is not going to make it either. however the hippo tang and the 2 clowns and the pajama cardinals look better today.
Yesterday the ammonia was never elevated only nitrites, I posted incorrectly. I have never had elevated nitrites before. In what instances are nitrites High when all other levels are normal?
I have saltwater aging wight now and plan to do another big water change tomorrow.
What I have learned is to always have plenty of supplies on hand, running out of salt was awful. I will also always double check the steps I take as I do my routine maintainance. I know people have said the fluval being left off couldnt have caused a problem, but that was the only other variable in all this.
Again, thanks for your input...I sure needed it.

 

[leigh]

So sorry to hear about your bum luck. In reading over your previous messages here is my hypothesis (in no way am I trying to be tang police or pin guilt--I'm just giving a run down hypothesis to try to explain timing and such)...I can certainly relate to the sadness as I had my own cucumber incident wipe out my tank...I feel for you...but my hypothesis:
Your tank size: 90 gal
Your inhabitants: yellow tang, niger trigger, dwarf angel, foxface, hippo tang, 2 percs, and 2 pj cardinals
Your tank was at best 'stretching' the limits on bioload. Last night you replaced the filters in your Fluval 404...my guess is a lot of beneficial bacteria had built up on those filters--perhaps you even (with your freshwater background) rinsed off the spongy parts--so in essence (while you meant to do the right thing by improving your filtration) you probably through out a large amount of your de-nitrifying bacteria...even just loosing a little amount may have been the straw that broke the camel's back, so to speak. Harsh as this sounds, I think with your bioload you were headed towards a tank crash. I do not think leaving the fluval off caused the problem, but instead I think the timing with changing your filters relates to loosing beneficial bacteria and thus prompting the crash.
It really is a bummer, I am sorry for your losses

 

[magdala]

Hi Leigh,
Thanks for your thoughts. When I was doing the filter changes, I did not change them all, I replaced 2 of the 6. I did not rinse any of the other filter componants with fresh water, I used saltwater from the tank.
The yellow tang was 4 inches, the Niger trigger was 3 inches, the foxface was very small..2-3 inches, the dwarf angel was 3 inches.

 

[leigh]

I still think it may have just been the little edge that pushed things out of whack. It really sounds like you did your best to control everything as much as possible--and I know you inherited this tank--I just think it's previous owner stretched it on bioload (standard rule of thumb is 1 inch per 5 gallons so for a 90 that's 18 inches--you had: yellow tang=4, the Niger trigger=3, foxface=2, dwarf angel=3, hippo=2?, clowns=2?, pj's=2? for a total of 18 and that's using the lower end for your foxface and conservative estimates for the hippo, 2 clowns, and 2 pj's) and while you've done your best to be cautious with it I think maybe just loosing the bacteria from 2 of the 6 filters was enough to start a chain reaction--all it takes is one fish to get stressed and die and then with that bioload the resulting ammonia spike could easily kill off the others. Sorry

 

[ophiura]

What was your pH and alk at the time, if measured? When you woke up, were the corals dead, or only the fish and the corals/snails died after time?
You see nitrites when you missed the ammonia spike when testing. In a mature tank, ammonia can be converted quite rapidly. In many tanks, there may be constant little spikes, but if people only test once a week, they may miss that moment in time.
Where are your power heads located? Any at the surface, or lower down?
Was the tank cloudy at all in the morning?
Personally, I don't think this was a biological issue...though it is possible...but the nitrite you are seeing is a result of the animals dying...not the cause of the deaths. I have seen animals survive very high ammonia spikes without die offs like that. Was this an established tank, with established fish? Did you feed after cleaning the filter? Have you done this before without problems??
Any chance something got into the tank? Buckets used for cleansers...any carpet cleaning, extermination?