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Water change temperature

Jaceree

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10 Jan 2021
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105
Location
Wales
When you water change what do you shoot for with regards to getting the temps to match the tank. Do you look to get it exactly the same or dont mind being a few degrees out either way? Im guessing having your new water roughly there will dissipate in the tank with no noticeable change in temperature.
 
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20 Dec 2019
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South Carolina
Within a few degrees is okay. I’ve matched my faucet to the tank with very small sharpie marks of where the hot and cold need to be. I change this when the weather changes because then the cold water comes out at tropical temps
 

hypnogogia

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6 Apr 2017
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642
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Oxfordshire
I heat mine with a spare tank heater, so it is more or less the same as the tank water, as I mix rain water with cold tap water.
 
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Jack B

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3 Jan 2020
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London
You don't hear many (any?) bad stories so I assume it's not that big a deal. Erring on the side of cooler seems more common than hotter. Mimics the effect of rain after all.
 

Courtneybst

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5 Sep 2016
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397
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London
I normally go 1-2c cooler. On the rare occasion my tap plays ball I can get a steady temperature that matches the tank water. Otherwise, I've worked out the ratio of warm and cold water I need to add to reach the desired temperature.
 

ian_m

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Eastleigh
This is what I use. Makes plant fiddling, bit of cleaning, emptying water onto front lawn and refilling tank about an hour to do.
Water change heater project.

I and many other people have often run cold tap water straight into the tank, remembering to dose dechlorinator into tank first, yes tank temp can drop to 15'C but fish don't seem to mind.
 

Jaceree

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10 Jan 2021
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105
Location
Wales
You don't hear many (any?) bad stories so I assume it's not that big a deal. Erring on the side of cooler seems more common than hotter. Mimics the effect of rain after all.
Im always reading about being careful of swings in temperature etc, but as you say it mimics rain. I would guess that water temperature in the wild isnt a constant either, but there's a fuss made of having a stable constant temperature. I dont know how many fish in the hobby could react to changes in temps...Discus maybe? i dont know.
 

Jaceree

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Thread starter
Joined
10 Jan 2021
Messages
105
Location
Wales
This is what I use. Makes plant fiddling, bit of cleaning, emptying water onto front lawn and refilling tank about an hour to do.
Water change heater project.

I and many other people have often run cold tap water straight into the tank, remembering to dose dechlorinator into tank first, yes tank temp can drop to 15'C but fish don't seem to mind.
Reading through the thread now.

I read this guy on another forums who said sudden changes in temp can kill fish, and affect their immune systems. On the face of it i would agree if you were to lets say do a 50% and pour freezing cold water in. Even then where's the evidence for that, as it seems to be passed around the hobby as a statement of fact, and we go along with it. Im more inclined to say ok fair enough how do you know it affects fish immune systems?...how do you actually test for that?
 

mort

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15 Nov 2015
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1,530
I just stick my finger in the new water as see if it's roughly the same, I don't mind a few degrees either way and nor it seems do the fish.

I think this is only really a problem if you are doing massive water changes with a dramatic difference in water temperature.

It's also interesting with regards to lower temps to stimulate breeding behaviour, as there are a few breeders I've come across that had fish that actually responded better to a slight increase in water temperature, so not all fish are created equal.
 

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