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I've had four unexplained fish deaths in the past several weeks -- in two separate tanks -- and I'm starting to wonder whether I'm looking at the beginning of a slow-moving but scary problem. I'm also wondering whether it could be related to tubifex worms -- and if so, what to do about it.

Here's the deal:

Tank A is a 55 gallon that's three years old with normal water parameters -- no ammonia, no nitrite, nitrates under 20 in both tanks. Temp is around 78 degrees. Ph is a steady 8.0. It gets 30-percent water changes and gravel vacs weekly. It's been more than six months since I added a fish to the tank. Until this week, it contained five rosy barbs, a dwarf pleco and six boesmani rainbows.

On Wednesday, I noticed that one of the juvenile rainbows was zooming around at the surface, almost like a shark, with her dorsal fin practically breaking the surface of the water. She wasn't gasping for air -- just sort of zooming around in circles. I planned to move her to a quarantine tank the next day, but by then she was dead. We looked at her closely when we pulled her out of the water, but there were no other visible symptoms -- no pineconing, no abdominal swelling, nothing.)

Cut to two days later. I go to feed the fish and everyone comes "running" except for one of the rosy barb females (who's about 3 years old, if that makes any difference). As the feeding frenzy commences, she comes wobbling out of a plant and I realize she's having some trouble with her equilibrium; wobbling a bit from side to side. She's still struggling this morning, so I'm planning to set up a hospital tank and move her.

Now for Tank B -- another 55 gallon in another room. That tank has three pearl gouramis, nine platys, and (until last week) five emerald catfish and three red irian rainbows. About a week and a half ago, during a gravel vac, a catfish came zooming out of a plant and flopped onto its side. When I tried to net it, it swam further, but kept flopping over, like it couldn't keep its balance. We ended up euthanizing it. Several days later, I came home from a business trip to find my 3-year-old female red irian -- who'd been acting fine when I left two days earlier -- floating.

In Tank B, water parameters steady and normal -- no ammonia or nitrite; pH a steady 8.0, nitrates about 20. It also gets weekly water changes and gravel vacs.

There's no possibility of cross-contamination between the tanks because they're in separate rooms, and I have separate buckets, hoses, etc. for each.

I have absolutely no idea what's going on, but I'm starting to wonder whether it could be related to some live tubifex worms that I fed them a couple of months ago. Some of the worms clearly escaped from the feeder in both tanks, because I've been noticing a bunch of them getting sucked up during gravel vacs, so I think they've been living and multiplying in the gravel.

FYI, those were the only two tanks to get the tubifex -- and I'm not having a problem in the four tanks that didn't get any. Could that be it? And if so, what do I do about it? Do I have to break down everything? I'm starting to get really worried -- I hadn't lost any fish in nearly a year, and then to have four go in under two weeks is scary.

All suggestions appreciated.

Although you feel that it can't be cross contamination, it does sound like a bacterial infection. It is very difficult to avoid the cross contamination, I know because I have tried.

My problem was not washing hands between tanks. It spread a pathogen very well...

__________
"To steal ideas from one person is plagiarism; to steal from many is research."
researched from Steven Wright

I suppose it's not impossible, but I'm just not sure how they'd get cross contaminated -- they're on opposite ends of the house, and I tend not to work on them consecutively. Plus, I use disposable gloves when cleaning the tanks, and I change them with every tank ...

Perhaps a toxicity that a test kit wont show? Anyone been using air fresheners, scented candles, fly spray, or flea killer in the house lately?

Have you been using any meds since the first fish died, and how long has it been since then? If were talking a few days its unlikely that its bacteria hitting so quick, if its been weeks then shouldnt you be using antibacterial meds?

Perhaps theres been a powercut and temps went off target and its taking a few days for the effects of shock to occur?

If the gravel has colonies of tubifex breeding in it , doesnt that make it dirty? Its possible that there are periodic ammonia releases, just cause you havent picked it up on a reading doesnt mean it isnt happening. If the filters working properly it will absorb the ammonia quite quickly , but perhap theres enough time for it to affect the fish. Perhaps its time for a gravel change.I know you said you gravel washed it, but I still remove the gravel in my tanks every 4 months or so, wash it thoroughly and put it back.

Theres a few things to look into there.

Last edited by longhairedgit at 07-Nov-2005 20:32