# Partial water changes - cold water supply



## Richard M (Apr 16, 2016)

Having got my tank and filter into a successful cycle, I'm now doing some PWCs (30%) to get the NO3 levels down, hoping to add fish later this week.

We live in a temperate area with chilly (although not freezing) winters, it's now close to winter here (southern hemisphere) and our tapwater temperature measures about 8 degrees C (47F), going down to 5 or 6 degrees C (42F) over the next few weeks.

I normally top up with a hose from an outside (cold) tap that sits just outside the window next to the tank; if I'm doing substantial PWCs, how do I minimise the temperature fluctuation caused by adding a significant volume of cold water? I'm finding that mixing in two buckets of hotwater from the hot tap seems to do it overall but moving 70-90 odd litres of water by the bucket will be a PITA.

Also with regard to PWCs, what is a reasonable proportion of total tank volume to change, assuming I do it weekly. Also is weekly about right or should I look at fortnightly?


----------



## nodima (Oct 3, 2002)

Can you set up a barrel, to fill with the cold water a day or two ahead, then put a heater in it? This could then be pumped out to the tank.

I generally go with 50% water changes - would be tricky to time the addition of hot/warm water to keep the tank consistent in your case.


----------



## tanker3 (May 18, 2015)

Nodima has a good idea. You can use a plastic (Clean new) garbage can, or a plastic storage container to heat/warm the water before pumping into your tank.


----------



## Richard M (Apr 16, 2016)

Yes, that sounds like the G.O.

I've got something that's just the ticket, (big black box that I keep my SCUBA gear in), can mix hot and cold water to correct temperature in there and then just pump it in - I have an old Eheim internal filter - can remove the foam from that and just use the power head to pump it out.

Thanks chaps - great ideas!


----------



## BillD (May 17, 2005)

Why not add directly from a set of taps that has hot and cold?


----------



## Richard M (Apr 16, 2016)

BillD said:


> Why not add directly from a set of taps that has hot and cold?


Because I don't want to add water until it's the same temperature or close enough to that of the aquarium, filling simultaneously from two supplies, one at 5-6º C, the other at 50º C at a rate and ration that keeps the mixed temperature at around 24ºC is going to be difficult; it might go over by lots or under by lots and either way, if it's wrong by a lot, it's going to take several hours to return to correct temperature range.

And not only that, if the fish are already in there, they are potentially going to be whacked by significant temperature gradients as temperatures change rapidly across short distances, whilst it's mixing, a bit like how it feels when you you up a bath with hot water whilst sitting in there..


----------



## noddy (Nov 20, 2006)

Richard M said:


> BillD said:
> 
> 
> > Why not add directly from a set of taps that has hot and cold?
> ...


Do you not have a tap in your house that has both hot and cold? Kitchen sink, laundry sink, bathroom sink etc...
I think that's what Bill means when he says "a set of taps that has hot and cold".


----------



## FishMaster43 (Feb 20, 2015)

I would strongly advise against using hot water from a HW cistern, especially if it has a copper inner tank which can leach copper sulphate into the water. Even though this is only in minute proportions it has the ability to build up and possibly affect your fish stock.


----------



## Richard M (Apr 16, 2016)

It doesn't - it's a rooftop solar system with a stainless steel liner.


----------



## dledinger (Mar 20, 2013)

I just put the cold water in, except for very sensitive fish. With most of my fish so long as I continue to do massive changes as the water gets cold they adjust well. Most of my tanks drop to mid 60s during winter water changes with no ill effects. The only fish I have that can't do that are Silver Dollars.

Other options:
(1) Change less water more often
(2) Fill very slow with heater on
(3) Supplement with pitchers of hot water while filling...that's what I do for the silver dollars.


----------



## Richard M (Apr 16, 2016)

Thanks to everyone for their considered advice; it's been very useful.

Richard M.


----------



## SrsSarcasM (Jan 28, 2016)

As has been mentioned if you have a mixer tap (can get a hot & cold mixture from 1 tap) then you can make your own connection from the tap to a garden or vinyl hose with just a few fittings from the hardware store and run this to your tank.

You can run the hose back into the sink while temp normalises and then the temp will be stable coming from your tap (unless someone in your house uses water, affecting the cold water pressure, or your hot water runs out).

This is preferable to dumping cold water into the tank and letting it heat up.


----------



## Richard M (Apr 16, 2016)

SrsSarcasM said:


> As has been mentioned if you have a mixer tap (can get a hot & cold mixture from 1 tap) then you can make your own connection from the tap to a garden or vinyl hose with just a few fittings from the hardware store and run this to your tank.
> 
> You can run the hose back into the sink while temp normalises and then the temp will be stable coming from your tap (unless someone in your house uses water, affecting the cold water pressure, or your hot water runs out).
> 
> This is preferable to dumping cold water into the tank and letting it heat up.


That's what I did in the finish - picked one of these up at Bunnings - http://www.gardena.com/au/water-managem ... door-taps/

I connected this to the laundry mixer tap and then fitted one of these - http://www.ladco.com.au/double-hose-connector

I then fitted the filling hose to one side, ran the h & c and adjusted to the correct temperature by running to waste through the unconnected side - once the temperature was in the correct range, I then flicked it over to the filler hose side and refilled the tank.

Worked really well - to empty, I simply siphoned the tank out using a large diameter hose run through an open window to a garden bed.


----------



## newcichlidiot (Jul 7, 2010)

Sounds about right! Have an awesome day.


----------



## Richard M (Apr 16, 2016)

SrsSarcasM said:


> .............This is preferable to dumping cold water into the tank and letting it heat up.


One other advantage of filling from the hot water tap; here in Tasmania, there's a multitude of different electricity tariffs; standard power from an electric socket outlet to run the aquarium heater etc is 26c/kWhr, hot water & heating tariff, which runs our hot water boiler, is only 15.7c/kWhr.


----------

