# will cold water changes hurt fish/bacteria ?



## Mr2Good (May 9, 2013)

i have Googled this question and haven't found a clear cut answer so Im asking here... My stock-list and aquarium details are in my signature... I do a %60-80% water change weekly on my tank and got tired of running from the tank to the faucet trying to adjust it by "feel" so i decided to just leave it colder on purpose.. i have all filters and pumps turned off and my water heater on during the process.. my temp of my tank stays about 78-80 degrees... after water change it drops to about 76... seems like my fish are ok almost as if they like the temporary temperature drop... my heater catches back up within a few hours...

question

#1. will cold water kill off my bacteria? i already made mistake of cleaning filter too well and went threw **** this week with daily water changes from a nitite explosion... mini cycle im assuming... wanna make sure im not doin myself my harm..

#2.. will the drop in temp shock my fish or stunt their growth? i have all juviniles 1.5-3 inches....some are starting to color up and tryin to spawn with females... lol...

my tank is in the photo below... excuse the cloudiness i just re-scaped it before water change.. (**** sand!!lol) any help would be appreciated


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## Fogelhund (Dec 3, 2002)

If the change in temperature in the tank is only 2-4F, it shouldn't be anything to worry about, unless you have particularly sensitive fish. That minor temperature change won't kill the bacteria, but there is the potential to do so if you are changing out 80% of the water, AND cleaning the filters at the same time. It is also possible that you could kill the bacteria, if you are not using a dechlorinator. I normally make practice to clean filters on different days than doing water changes.


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## Mr2Good (May 9, 2013)

i made the mistake of cleaning filter and tank at the same time last week.... boy ill never do that again... went threw a mini cycle i had to fight with daily water changes... last night my nitrites went back to 0 again... so i survived it without a casualty lol . worst part was the filter wasnt even that dirty imma wait about 4-6 months before i clean it again...

I use water dechlorinator with stress coat in it... i add it to water before i fill the tank back up... i have researched alot on the forum about the right way to do it.. so im pretty solid on that... just the temp thing was the big question... seems like im safe...

give or take the amount of water im changing.. ill drop it to %50 weekly again... was doin %80 during that darn mini cycle...

does the cold water stimulate fish to spawn?? i notice them dancing infront of females alot after a water change... the tank becomes very lively...


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## nodima (Oct 3, 2002)

I'd be thrilled if my water changes were always within 2 degrees.

You have little to nothing to worry about temperature wise with those numbers. As far as it's impact on spawning, every time the water is changed in my Tropheus tank, it stimulates spawning behavior. It seems to be more related to new water than to temperature. However for some fish such as corydoras catfish, a known method to stimulate spawning is a water change with 10 degrees or more cooler water - this simulates spring rains.


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## Mr2Good (May 9, 2013)

i hear ya man.. its tough to judge without some kind of digital thermometer... i have noticed using the cooler water leaves my tank looking extra clear and crisp...maybe its coincidence.

when i cleaned my filter i used old tank water that i left out in a bucket all night... thats another mistake i wont do... water in the bucket was freezing cold... thats why i had my mini cycle.. killed off bacteria that way... moral of story is once u start a project dont wait till next day to finish it lol...

did have another question i been fightin with... i have alot of surface agitation... but there is one dead spot on the surface that appears to have dust floating on top of water... ether from sand i stired up or from the NLS pellets... any remedies to get rid of it besides another powerhead? ....


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## anthraxx4200 (Aug 16, 2012)

i have a friend who does nothing but cold water changes, after a long debacle with the local water company and a TON of testing, they found that the hot water tank would actually release all sorts of harmful metals that collect and just sorta hang out inside it. even with rinsing the thing out it still persisted. so he just started doing cold water changes and it seems to be working (he breeds ca/sa like its going out of style, were talking close to a hundred different species and nobody is affected by it) i know it just doesnt make sense but it works. anyhoo GL to ya.


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## Mr2Good (May 9, 2013)

anthraxx4200 said:


> i have a friend who does nothing but cold water changes, after a long debacle with the local water company and a TON of testing, they found that the hot water tank would actually release all sorts of harmful metals that collect and just sorta hang out inside it. even with rinsing the thing out it still persisted. so he just started doing cold water changes and it seems to be working (he breeds ca/sa like its going out of style, were talking close to a hundred different species and nobody is affected by it) i know it just doesnt make sense but it works. anyhoo GL to ya.


thants some great info man.. appreciate it.. ill keep on wit my routine


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## cichlid-gal (Apr 27, 2012)

anthraxx4200 said:


> i have a friend who does nothing but cold water changes, after a long debacle with the local water company and a TON of testing, they found that the hot water tank would actually release all sorts of harmful metals that collect and just sorta hang out inside it. even with rinsing the thing out it still persisted. so he just started doing cold water changes and it seems to be working (he breeds ca/sa like its going out of style, were talking close to a hundred different species and nobody is affected by it) i know it just doesnt make sense but it works. anyhoo GL to ya.


I believe he changes 25-30% of his water 2x a week. He has big tanks too.


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