Carbon monoxide poisoning?

[Woody]

I might have just made a really stupide mistake. I set up a 5-gallon treatment tank on a shelf in my garage and began using Neosulphex to treat a mature dwarf rainbow with a fungal infection. I soon added an immature dwarf rainbow that was behaving strangely (hovering near the surface), hoping to protect the other fish in my primary tank. I moved the tank into the garage last Saturday and it was placed about 5 feet above floor level.

The hospital tank was clean with water conditions in the normal range and I was using a power filter with the carbon filter removed. Just as the mature fish seemed to be recovering, he turned up dead two mornings ago. This morning, the younger fish was dead. My wife suggested that the water might be absorbing the carbon monoxide emitted from our cars -- we never idle them in the garage, but we pull them in and out a time or two each day. There is also a gas-operated hot water heater and boiler nearby, but both are new and have been tested in recent months. Any emissions there should be minimal, but perhaps they could still be enough to cause a problem.

The carbon monoxide idea sounds plausible, which makes me feel like an idiot for moving them to the garage.

 

[LoveMyOscar]

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[Woody]

Good questions. I should have mentioned that the garage is insulated and heated. The air temperature is probably in the low 60s (Fahrenheit). The tank is also warmed by a reliable heater -- I immediately confirmed that it was working after the first fish died.

The air exchange isn't too dramatic when the cars move in and out of the garage, but maybe it's enough to cause the problem.

In any case, I'll be removing the treatment tank from the garage tonight. I would like to solve the mystery, though.

 

[LoveMyOscar]

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[sinistral]

I sincerely hope a real chemist posts a reply to this. My first question as far as if the 5 gallon aquarium might be absorbing CO emissions from your vehicles is: how soluble is Carbon Monoxide in water? I may not be a chemist, but I can search the internet, and I discovered from multiple sources that CO is "negligibly soluble" in water. In fact, only 0.00270 g CO dissolve per 100 mL H2O at 20 oC. Furthermore, this suggests that even over time only minimal amounts of CO would be accumulating in the aquarium.

I've been poking around on the internet but I can't find a reasonable estimate of how much CO your vehicle is likely to emit in terms of parts per million or percentage over time, so I can't figure out how much exposure your tank would be getting to CO. Common sense however tells me that the level of exposure given the conditions you've described would be minimal.

I can't emphasize enough that I am not a physical chemist, but given this preliminary data I would expect it unlikely that CO is the cause of death in your fish. I hope that an engineer and/or a physical chemist will wander along and point out to me the things I don't know so I can learn more about this, as I think it's an interesting question. I wonder, for instance, if there are other harmful emissions that might be more soluble in water...

It does seem more likely though that what killed your fish was the initial illness. What's that medical saying? "When you hear hoofbeats on the range, think horses not zebras..."

 

[Woody]

Interesting findings on the CO/water issue. I agree that the original disease would be a logical place to look, but the adult fish was looking better than he had in two weeks. Only a trace of fungus remained on his body. The immature fish had no visible symptoms; I moved him into quarantine because of the odd hovering behavior (which sounds like a possible ammonia problem, based on another posting in the beginner's forum, but ammonia tests at 0 and all other fish are thriving).

One other possible clue, if anyone sees something in this: Neither fish was a floater—both were found at the bottom of the tank, their bodies slightly curved to the side, as if making a turn while swimming. Probably means nothing. I've found dead fish at the bottom before.