overheated tank :(

[twinkles]

Woke up this morning and checked the fish, and one tank was superhot and all the danios dead

Heater was going still so i guess the thermostat is buggered. I got it with the tank a few days ago, temp's been fine till now. Water was about 30 deg, have taken the lid off and opened the filter to let it cool slowly, heater is out and i've put another one in that i know works well. There's a couple of baby whiptails in there, they seem fine thankfully, but is there anything else i should do? Put a little bit of cold water in but don't want to make it cold too quickly.

I guess the lesson here is not to trust second hand heaters, will buy new from now on. It was only a 50watt, if I hadn't of done such a thourough job insulating the tank they probably would have been ok.

[lmsmith]

Aw, I'm sorry for your fish!

I'd only be concerned about bring the temp down slowly, you don't want to cause them more shock by dropping the temp quickly.

[smidey]

are danios are fragile to higher temps normally?

my african display often gets over 30 in winter when the fire is going & i have never lost any fish with a higher temp.

[twinkles]

apparently so, recomended temp is lower than for most tropicals. I think they would have been happier without a heater at all

Catfish seem fine, happy as, temp is almost back to normal. Shame about my pretty danios though

Getting a big tank next week, so will get some more once its set up.

[lmsmith]

Yeah, some tropicals can stand high temps, I've had guppies up to 34deg with no probs, but I guess there are some out there who are more low range tropical.

[Dixon1990]

Ive had dwarf flag cichlids up to almost 40

[whetu]

It would depend what temp the danios were used to. They can certainly live at lower temps than a lot of other tropicals, but can also be very hardy at higher temps if they are acclimatised slowly. I think, as twinkles said, the extremely well-insulated tank probably meant the temp rose pretty fast once the thermostat failed.

Sorry to hear about your losses, twinkles. It's so hard when you're trying your best to do what's right for your fish and it all turns out badly instead.

Just to make sure this lesson is not wasted, please will everyone reading this thread go and check the temperature of your tanks! And if you don't have reliable thermometers, go out and get some!

*runs off to look at tank temp*

[whetu]

Further to the danio-temp-issue, I have (in the past) kept danios with clown loaches at a temp of 27 - 28 dgrees. It wasn't ideal and I did notice that if one of the danios got a minor injury it would fungus up very quickly and require treatment (in cooler temps if they got a minor injury they tended to recover just fine without meds). So obviously the danios were being stressed at the higher temps and it was not ideal, but I suspect they would have withstood an overnight temp increase of a couple of degrees just fine.

So once more it supports the theory that a sudden change in conditions is a bigger issue than long-term slow adaptation to stressful conditions. (Think temperature, pH, etc)

[twinkles]

Yes, i think the heater must have come on in the wee hours and stayed on, temp would have gone up fast, the thermoteter only goes to 30 so could even have been hotter, felt like hot bathwater. It was 25-26 the night before so quite a change.

I can see the sense in having several smaller heaters in big tanks, will be doing that when i get a big tank set up.

And not using second hand heaters without testing them for a few days first.

They were glowlight ones too, i did read somewhere they're a bit less hardy than zebras.

[twinkles]

good advice, i'll be passing that on too lol.

Heater was fine at first, must have jammed or something.

[suphew]

It's more likely a problem with lack of oxygen, 30 degrees isn't that high but as temp goes up the oxygen level will drop. Add some water movement, some air stones and/or power heads.

[twinkles]

its got a 400L/h filter, with a trickle bar thing the water comes out of, lots of movement i thought?

[twinkles]

oh and tank is 40L

[twinkles]

was looking at one of those big airpumps to run bubble walls or sponge filters in all our tanks, but i thought the filter in this one made enough current and splashes by itself? I guess i could put one in it anyway.

[suphew]

In normal circumstances that's proberly more than enough. But with the extra heat strange things can happen, and it could just be the sudden change rather than a complete lack of oxygen. Even aside from the direct affect on the fish, the bacteria in your filter would have suddenly been getting less oxygen, as well as the change in temperature, it's possible you triggered a mini cycle in your tank. Which might be what affected the fish so drastically.

But really this information is now just useful knowledge for the future (if your ever unlucky enough that this happens again). Your temperature should be back to normal now, so all you can really do is a water change in case your ammonia etc levels have gone up.