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I had one of those glass thermometers that go inside the tank and have little grey balls and a red liquid in.The thermometer came away from the side of the tank, floated off, hit the side of the tank causing the glass of the thermometer to break and the little grey balls to spill out. They have all gone into the gravel and cannot be seen. Are they harmful to the fish?

the red liquid is alcohol... no problem, except maybe a little drunken stupor tonight for fishie.
don't worry about it.

Well, I'm pretty sure those little grey balls, as you put it, are just miniature ball bearings, used to weigh down that half of the thermometer, not mercury (perhaps rusting if nothing else). On the other hand, the red fluid is alcohol, which is potentially harmful to fish, but in such a small doseage, I wouldn't be too concerned (depending on thesize of your tank). Maybe a water change and a quick gravel vaccing would help. And for future referrence, I'd stick to the sticker thermos which attach to the outside of the tank.

Last edited by Cup_of_Lifenoodles at 26-Sep-2004 16:23

Well it shouldn't be too harmful since they are specificly made for aquariums. I have the same floating thermometer. Just do a partial water change as mentioned and a gravel vac. I also have one of the sticker thermometers and they arent THAT accurate.

I bet the manufacturer expected that to happen to somebody and made the stuff non-toxic.

Sticker thermomitors are very inaccurate...they can be off by several degrees. They don't measure JUST tank temp, but the room temp, AND tank temp.

I'm going to put a floating thermomitor in one of my tanks with a sticker thermomitor and compare them. I'll post up the results in a while

Another trick for you to use is to take a magnet and run it through your gravel. This should pull most of the ball bearings out. Then you won't have to worry about rust.

I put 2 different brands of floating thermomitors in the tank (Penn Plax, and Aqua Culture were the brands I believe. They don't say what brand they are on the thermomitor itself, but I remember buying 2 different brands at the store when I got them). I've got a sticker thermomitor on the tank too...but I forget what brand it is because it doesn't have a label on it either.

Both of the floating thermomitors read 81 degrees F. but the sticker thermomitor reads 83 degrees F. There's a 2 degree F difference between the floating thermomitors and the sticker thermomitor.

Solution to the problem: Get a GOOD suction cup to hold the next floating thermomitor to the tank, and/or put a plastic mesh around it so it won't float off and break. Another solution: keep the thermomitor inside your filter, in a place where it won't get broken (such as behind the filter media of an HOB filter). It won't float off and get broken on anything

Thanks for the advice, all the fish seem okay except for a neon tetra who looks a bit wobbly but that could be coincidence. I will try the magnet trick to see if I can pick up the little balls.Have now bought a thermometer with just red liquid in, no balls!