Weekend death toll

[stoneydee]

I maintain a 37 gallon freshwater tropical fish tank at work. It's been running for about three and a half months now, and everyone just loves it.

Came in to the office from the weekend, and we had five dead fish (two goldskirt tetras and three emerald cories) and two dead dwarf African frogs. I had done a water change on Friday (I try to do them before leaving for the weekend, and fast the fish after the Friday afternoon feed till Monday morning), all levels were 0, and everyone was fine and doing their thing.

I fished out the bodies and did a water change, vacuuming the gravel well, since ammonia was at 2 (no nitrites, .5 on nitrates). None of the deceased appeared to have been slaughtered, although one of the tetras was beginning to decompose. One of the surviving angels looks like it has some deterioriation on the pectoral and tail fins, but not like they've been nipped. I've added melafix, and the only thing I can think of is that it is bacterial, but how?

I've explained several times to the housekeeping staff about not using any chemicals on or around the tank - they swear they don't. I wash my hands in the hottest water I can stand before I do water changes or feed. I only wipe the outside of the tank with damp paper towels.

Any ideas on how a tank in good condition on Friday could go south that fast?

 

[ferret]

Not sure, but you say your levels were all 0, but in the next sentence state that the ammonia was at 2 and the nitrates were .5..

Nitrates are perfectly normal, but ammonia isn't. A 3 month old tank with no recent additions should have 0 ammonia unless something killed off the bacteria. The ammonia would also have to be extremely high to wipe out so many fish in so short a time.

 

[stoneydee]

Sorry, I should have explained better. Levels were all 0 on Friday after the water change and up this morning when I came in and found dead fish. I assumed ammonia was up because of the dead bodies.

 

[ferret]

That's a possibility. Did the water have any odd odors or discoloration?

The only things I could think of are disease (Unlikely without any recent additions and so quick a death) and as you've partially assumed, some cleaning materials..

I'd look for the bottle of windex..

 

[stoneydee]

Oh yes, it had an OMG-that-has-to-be-the-tank smell. That's why I went straight in there when I was coming down the hall. Made me wonder if the fish had been dead all weekend.

 

[QTOFFER]

Any chance there was a power outage that stopped the filter? A full day without water surface agitation would cause havoc. This also could result in some degree of kill-off of the biofilter.

 

[astroguy]

Or maybe somebody fed them way too much behind your back?

 

[stoneydee]

I hadn't thought about power failure. That should be easy to check. I don't think it was feeding, because they are fasted on weekends, and generally, there's no one at the office then. The two diehards who come up here every once in a while hardly ever pay any attention to the fish, so I doubt they'd feed them.

It's just a puzzle for me, and I'm hoping we don't lose any more.

 

[QTOFFER]

It may turn into a big fishy mystery. As astroguy suggested, maybe they were overfed. Perhaps someone brought their kids into the office over the weekend. "Mommy, look at the fishies...they look hungry!'

Still, I wouldn't think overfeeding would turn the water parameters sour that fast....
I'm still going with the power outage scenario. Hope you find out what was the cause.

 

[Allivymar]

Bummer And I HATE mysteries.

Its possible originally one animal died, and the resultant change in water chemistry did in the others. I wonder about other chemicals because of the frogs; they are especially susceptible to toxins. However, they are also pretty delicate overall and often die for no reason as well.