Are Our Fish Too Warm?

Very interesting article here...

http://www.seriouslyfish.com/whaddaya-mean-too-hot/

... suggesting that the temperatures given in the books and websites are actually not very accurate, and refer to pretty much maximum summer temperatures that the fish only encounter temporarily.

I'm a little concerned that we need to obtain accurate data before arbitrarily cooling down our fish, but it seems that we are keeping most if not all of them way too hot, which keeps them permanently stressed and therefore prone to diseases...

I remembered something on this subject a few years ago - it turns out to have been 5 years ago. It is worth reminding people every so often.

After it was raised before, I turned the heater in my main tank down to keep the water at 23 deg C. The fish have been fine ever since. I do appreciate that this might still be too high though.
Looking back at the 5 year old thread, I see that I once forgot to turn my heater back on after a water change and looked at the thermometer after noticing 4 days later that the fish were all lying on the bottom of the tank - 19 deg C. This is why I do still use a heater and have it set to keep the water above 19 deg.

Interesting article.

I may have got this wrong, but I understood that it is the fluctuations in water temperature that cause river fish to spawn. It was several years ago that I researched it, for south Asian fish. (May even have been the same thread @Sue mentioned) And my limited experience backed up some of what I'd read. In south Asia, they have monsoon season. The weather gets warmer and the rivers start to dry up (water level reduces). It makes sense that at this stage the water temperature is also increasing. Then the rains arrive and there is a huge amount of colder water entering the rivers. The water levels rise and the temperature drops. Then the fish spawn.

Whenever I did large (50%) water changes, my cories would leave eggs everywhere. But they didn't breed continuously, pretty much only a few days after I'd done a large water change.

I have recently tweaked my heater down a degree or so. With continuous temperature monitoring / recording, I could see that where I thought I had the temperature set at 25°C, it was actually fluctuating around 25.5°C. It now fluctuates around 24.5°C, and never goes as high as 25°C.

I measure the temperature at the opposite end of the tank to the heater, but the water temperature is still warmer than the setting on my thermostatic heater.

It is not uncommon for a heater to read the temperature inaccurately which is part of the reason why thermometers are so popular. Now I have my heater set to the temperature I want, regardless of what it actually says(!), the thermometer rarely gets used as I will soon notice if the heater fails by touching the tank glass or observing the fish, as Sues experience shows. I do recalibrate every now and then as I have found my heater has drifted with age. The heater I have or my 220 litre tank actually has the ability to calibrate the temperature dial to show the true temperature as read by the user in the tank.

Sues experience may discount my theory about nighttime temperatures - a drop of 4 degrees seems to have been too much for the species in her tank at the time which is not a huge amount (a water change could presumably have the same affect). That said it is likely to be lower than the stated ranges for the fish, so there clearly is some validity to these...

my head hurts a bit now... I agree, this is a complex topic to understand with lots of conflicting information... I think I will compare the temperature ranges given for my fish at different sources tomorrow to see what I can discover...

I've also had a situation where I've moved fish to a different tank, things have taken longer than expected, and I've left the original tank until the following morning to strip down completely, only to find a lone straggler that I had missed pottering around in about an inch of water after coping with no heater or filter overnight. Obviously this was a massive mistake on my part, and not something I would wish to repeat, but the little fella survived the ordeal and is still with us.

When you consider the fluctuations that the fish must tolerate in nature, I'm more amazed that nobody has manufactured programmable heaters.

Yes it does.....but imagine being able to recreate a more natural environment for your fish....perhaps one of the down sides would be increased breeding and being over run with babies on a regular basis though. 

Fair point about the time taken to drop the temperature on a larger tank @Helen
It's such a problem on my axolotl tank that I had to buy a chiller.