All of my fish died the day after a water change

[elpezgrande]

The day after I did a 6% water change (about 3 on a 45 gallon) all of my fish were gone (2 false percs, 1 royal gramma, 1 purple firefish). The the only body left was too far gone for me to get a clue about what had happened. I tested my water and the levels weren't pristine, but the were only a slightly off color match for the lowest range of my tests (i.e. they were closer in color to the lowest range than the next higher range).
Temp 79, Sg 1.025, PH 7.9, Ammonia 0, Nitrite < 0.3
It only seems to have been the fish that were effected, my shrimp, snails, crabs, feather duster and BTA are still alive. The water that I used for the change was premixed RO/DI water that I got from my LFS. I had previously used 2 gallons from the same jug in another water change with no problems. The remaining 3 gallons that seem to have caused the problem were sitting in the jug for about 2 - 4 weeks. There had been no other changes to the tanks for at least 4 weeks, which is about the time I got the purple firefish.
I think the best thing for me to do is assume that it was a fish disease/parasite of some kind and wait at least 4 weeks before getting any replacement fish. Anyone agree or disagree?

 

[beth]

I can't see a water change causing nitrite. The problem is the nitrite. How old is your tank, and has anything died in it that hasn't been removed? Is the dead fish left in the tank the cause of the nitrite?
Was the water dechlorinated? What water are you using? Is a fish diesease a possibility? What were the fish symptoms prior to death?

 

[elpezgrande]

Thanks for the reply Beth, why do you think nitrite was a problem, is that something that will kill fish before inverts? According to my tetra test kit < 0.3 is the lowest value for the nitrite test, so I wouldn't think it was severe. The sample color did appear to be between the colors of the < 0.3 range and .03, so I wouldn't say it was 0 maybe .10 - .15. As far as symptoms, it was rather sudden, I went from normal tank one day to the next noticing that my fish were all missing. I only saw 1 body, and that was being quickly devoured by the cleanup crew.
The tank's age is a tricky question. In theory it is 1 1/2 years old. 2 months ago I upgraded from a 30G to a 45G, switched out the CC for LS and added some more base rock. The water I used was premixed RO/DI water that I get from my LFS. It should be pretty clean and I have used water from this LFS since I started my tank. I just can't imagine what would take down all of my fish at the same time. If it was a disease or parasite, it seems like they wouldn't have all died at the same time, not to mention the fact that there really wasn't an event that could have introduced a disease other than adding the purple firefish 4 weeks ago.
One other potential suspect is a fire shrimp that I got about 1 1/2 months ago. I think it is aggressive because I saw it trying to attack a snail with a ferocity I have never seen from a fire shrimp, and shortly after getting it my 2 cleaner shrimp went missing. However, it isn't more than 2 inches, so I'm not sure it could take out all of those fish. Plus, it is the one invert that seems to be missing along with the fish, but it has always been good at hiding in the rock work.

 

[mwaraxa]

Well i find it very unlikely that your fireshrimp killed any fish especially all of them in ONE night. Your water levels didn't seem too crazy either. Again, to kill everything in ONE night. MY guess would be you maybe got something stupid on your hands or in your water jug or something and got it in your tank when you did your change. . . . I can't tell ya how many times i come home from work and put lotion on and then start fooling around with the tank an hour later before i slap my self and go wash my hands. just throwing the idea out there.

 

[beth]

I think something probably died and caused a spike in ammonia and nitrite. By the time you tested, all you were getting was the nitrite. But, by that time the fish were dead. In an established tank, ammonia can raise and fall back to normal within just a few hours.
At this point, we can only guess what happened. To be safe, I would leave your tank fishless for a month.
Also, a test kit should have a zero reading for nitrite. Nitirite is harmful to fish, even trace, and can kill fish. A trace amt is not likely to cause a massive wipeout, but, as I suggested, there could have been an ammonia spike wo your realizing it. Find a test kit that reads zero. Selifert is a good kit for reefers.
Is it possible that you a mantis shrimp in your tank?

 

[elpezgrande]

I don't think a Mantis is a possibillity. I haven't heard any clicking, and the only thing I have added since upgrading to a 45G 2 months ago is live stock, none of which were mantises, dead dry base rock, which couldn't be hiding a living mantis, and 3 bags of aragalive sand. I doubt a mantis could survive in a sealed bag for weeks, surely it would run out of oxygen sooner or later.
I suppose the most likely explanaition is an ammonia spike. I will take your advice and hold off on new fish for a while and see about getting a better test kit. Thanks for all the responses.

 

[beth]

You might want to set up a QT while you're waiting on the restocking your tank.

 

[babs]

I have a question, I am having a problem with nitrate, not nitrite. I have de-nitrate in my filter, but it's not going down, it's close to 20 now and has been higher. I use lfs water, and i also have lost stock, one problem i was having was my top off water. I was using my tap (well) water and it's high in nitrates.
Does anyone have another way to get it lowered.
and the one that started this thread, could the NITRATE level be one of your reasons for the deaths. Just thought i'd ask, since i know it probably is one of mine.
Hope your tank is better.

 

[oreo12]

I wounder could they have sold you the water from there water change? That is what a lfs around here dose. I myself have a 12 year old 29 gal tank I never do water changes. just top them off. I add aditives for the corals have been have good luck have xinea making more xiena a tree coral making more tree corals feather dusters that have been in there for a long time don't even rember when I got them. But I would wounder if they sold you some water that came from there water change and maybe it was high in nitrites? (not saying you should not do water changes things that work for one might not work for another)