Random thermometer question...

[AyalaCookiejar]

So, when you buy an aquarium thermometer they usually have those little black beads and then some red stuff (haha) directly above them. I've noticed that that red part often fades when the thermometer is old to like a light orange color. Why does that happen? Could it indicate that the thermometer should be replaced? Do you ever need to replace a thermometer?

Lol I know this is totally random.

[WhiskeyHands]

These thermometers have never worked for me. I always end up buying another one i put in the tank

[Firefly85]

interesting question, I have always like these thermometers the best tho, no real answer for you, i had to replace all of mine when i started the hobby back up because either he old ones got thrown out because of the bad illness that wiped out all my guppy breeding stock around 1999 or broke during the move.
I hate the stick on the side of the glass ones as they always seem to be a couple of degrees off, or stop working after a few months.

[Myates]

I love those type of thermometers as well.. most likely it's due to age or exposure to light. The only danger is if you break it - obviously the mercury, but those beads could fall and choke a fish.

But an intact one is safe to use, never needs to be replaced.

[inuudo]

If the liquid in the thermometer is red, it is not mercury. In fact, aquarium thermometers haven't been made with mercury for quite some time now. The red liquid is alcohol based, I believe. The metal balls could be problematic, but I don't think they contain lead -- I broke a thermometer in a tank once and immediately scooped out as much of the substrate in the area as I could. I found some more of the balls a couple of weeks later and they were rusted, so that indicates they were made of steel.

And now, having said all of that, I will confess that when I broke that thermometer my very first thought was OMG Mercury!!! Get the fish out! Break down the tank!!! And that is what I did BEFORE googling. Oh well, now I know I can break down and rebuild a 25 gallon tank in just over one hour.

[AyalaCookiejar]

But wouldn't something alcohol based burn the fish? 0_0 as long as I won't need to replace these again soon. I just bought 4 more so now I have 6 and I only have four tanks :p otherwise I have to drive an hour to buy one because Walmart and their warehouse here has been completely out of aquarium thermometers for over 2 months.

[WhiskeyHands]

Originally Posted by inuudo

The red liquid is alcohol based

Next thing you know your fish is drunk.

[inuudo]

Originally Posted by AyalaCookiejar

But wouldn't something alcohol based burn the fish?

I don't know about that. It's not ideal, but you would be doing a water change immediately anyway.

I have taken the glass thermometers out of all my tanks now because that accident freaked me out so much. I bought digital thermometers for the 37 and 45 gallon. In my two smaller tanks (20 and 10) have metal thermometers that hook over the edge; they still have the glass bulb but are much more protected from breakage than the floating glass ones are.

[Shadyr]

I imagine the red is wax that is used to seal the weights in the tip of the housing, and it like most things just fades with exposure to light.