Partial water change - temperature??? Pet of the Month
🐶 POTM Poll is Open! 🦎 Click here to Vote! 🐰


New Member
Jun 19, 2003
Reaction score
:huh: Hi,
Does anybody have any tips for maintaining water temp during a partial water change? I've changed my 5 gallon Betta tank twice, and all three times I just couldn't get it right -- even though I bought a second thermometer to check the new water.

I keep Horatio's tank temp between 78 (at night) and 81 during the day, with the norm usually being right at 80.

First time I did a partial, I got the new water too cold and he had a bit of shock. The second time, the water was still cooler but not enough to cause shock. Yesterday, I got the water too warm and it stayed at 83 in the tank for quite some time and I couldn't get the temp back down to 80. I had placed the jug of spring water in a large pan of water on the stove set for low temp, and gradually brought the temp up to what I **thought** was 80 degrees.

There has to be a better, more accurate way!

Any suggestions???

When I change the water in my tanks I always feel it and try to make sure that the temp feels about the same if not a bit warmer. It is of my opinion that fish dont care for cooler water but water thats a little warmer they dont seem to mind too much. Either that or I got some strange

I let my water stand for 2 days treated. Room temp seems fine for my fish.

Hi sef

Fish can withstand quite large fluctuations in water temp.

I do not recommend this, but , When I do a water change on my display tank, (88 UK galls @ 86F) I gust drain 25% of the water, then refill strait from the tap, slowly. The tank contains discus, and I do not do anything which will endanger them, IMO.

In the past I have, this was by accident, dropped the temp in a tank by 15C when doing a water change, and the fish still survived, these were Angel fish.
Hi, thanks. I should have added that I keep a heater in his 5-gallon tank, so trying to get replacement water (I can't use tap water; it has too much ammonia so I'm using bottled spring water) up to the right temp is a REAL challenge.

Not only that, but the heater seems hard to regulate. Horatio's tank was reading 78 this morning (which is a little cooler than he likes it), so I slowly adjusted the heater so that it would increase up to 80. We left to go somewhere and came back to find the tank temp at 83 or slightly more!!!! Now I'm trying to slowly get the temp back DOWN to 80. It seems to be a constant balancing act.

The reason for the heater is that we **usually** keep the house quite cold inside. Today is unusual, as we're having a semi-nice day out and have the windows open. It's a little warmer in the house than usual, so I think that's why the tank is getting too warm.

Does anybody else run into this? :/

Most reactions