Water Change Temperature difference

[Danio8]

I recently took in a male betta fish that was unwanted. It is still in the original 3 gallon tank with the gravel and everything. I added a heater (which keeps the tank at about 78 - 79 f) and a sponge filter to the tank. Everything seems to be going well. I just did a water change and realized that in such a small tank, doing a water change with room temperature water lowered the temperature down to around 72 f. I hope the betta will be okay from the shock! Anyways, Does anybody have any suggestions on what to do?

[Aiken Drum]

That should be fine. But mix hot + cold water from the tap to match the water in the tank.

[Colin_T]

A temperature change of a couple of degrees is not normally an issue. A lot of fish have to deal with this when it rains in the wild. They get a sudden influx of cooler water. Corydoras usually spawn after a big water change using water that is a few degrees cooler than their tank water.

If you are concerned, just add a bit of hot water or boiled water to the bucket of new water when you make it up. Get the temperatures closer so there is less difference.

[Joe_D]

What I do is to prepare 2 gal of water a day in advance in gallon jugs for my weekly water change for my 10 gal tank
I just feel the water to judge the correct temp. :

I keep the temp in my apartment somewhere in the mid 70s f as I do not pay (separately) for heat.

Anyway, by the next day the temp in the jugs is close enough to put in the tank
As an added benefit it makes easier to change water by braking up the change like that .....preparing the water a day in advance.

BTW in the summer I set the AC to make it about 75 f ::

[m.j.gomez]

Hello, I used to test temp w/finger thinking it was close enough as to not harm pets. Then some of my cory catfish getting blisters on them. Found out it was gas bubble disease caused by adding to cold or hot water to tank. Bought a quick read thermometer & never had problem reoccur. In severe cases it can cause internal damage too. Hopefully this helps!!!!!

[ADsnail]

A few times over the years we've had sudden seasonal changes, going from 81º one day to waking up with the outside temp around 63º the following morning. The indoor temp reflected this. Jumped up with a start to realize that the tanks may have dropped significantly too. And finding the bettas in 69-71º. Of course I worried as I plugged in the heater as fast as possible. But they were fine - they just stayed in bed (the log) the same as I do when it's cold in the room. As soon as the heater brought water up to 74 or higher they became their usual active selves.

[Danio8]

Ok, Thank you for all the input!