Water Temperature

[Schmill]

Ok so my question is, how low can you let the water temps go in your tank?

My tanks are normally at the 23-25 deg C temperature range. However I am thinking about water changes...
Many many people on here will say that the cool water is good for the fish, it simulates rainfall, it can stimulate spawning etc etc. however other people seem to say that altering the water temperature in a tank can stress your fish. I'm sure I've seen it written on here somewhere that a sudden change of just 2 degrees is enough to upset the fish?

I'm just wondering HOW cold you can let the water go, and for HOW long?

I had previously intended to fill my tank from a hot/cold mixer tap, but none of the tap adaptors seem to fit it, so thats out.

In the summer I don't imagine it will be too bad, as even the 'mains' fed cold water is more of a mild cool / warm temperature, however at the moment the weather is obviously getting colder, and hence the water from the underground pipes is also colder. I did a 100% water change on my cycling tank at the weekend, and once I had refilled the tank from the mains the water was cold enough to completely numb my arm after just a few minutes of 'fiddling' with the tank contents, (I think it was around 5 deg C).
Obviously 100% water changes are not something I intend to do once the fish are there, (unless there is a MAJOR issue), but perhaps up to 50% could still be changed in one go.
Do the temperature changes happen linearly? As in if my tap is at 5degrees, and the tank is at 20 degrees, and I changed 50% of the water, then the final temperature would be at 50% of the difference (12.5 degrees) ?

Thanks

 

[smegforbrains]

As in if my tap is at 5degrees, and the tank is at 20 degrees, and I changed 50% of the water, then the final temperature would be at 50% of the difference (12.5 degrees) ?

The best way I have found is to run hot and cold taps into your bucket and use a thermometer (or in my case a multimeter with temperature probe) to get the water within a degree or two of the normal tank temperature.


You will be surprised how well even a small 60 litre tank can hold it's temperature, even if only half full.


Providing your house isn't freezing cold, what is left in the tank while you are changing, shouldn't drop by much more than a degree

 

[saz326]

I dont mean to put a spanner in the works straight away - but why perform such a drastic water change...?

If it is simply to reduce Nitrate etc in the tank then maybe you could introduce plants that would help and minimise the amount of water that needs changeing. Certain fish ofcourse dont go well with plants so you may have no option than to do the water change... just a suggestion on the side that could prevent you doing too much work!

If you are thinking of running the water into the tank by hose, then can you allow it to trickle in?

Its not the temperature change that stresses the fish in most situations - it is how FAST the temperature change occurs. If you dump gallons of freezing water into the tank, then of course the fish wont have time to aclimatise to the temp drop, but if you add it litre by litre and the water circulation mixes it in quickly then there is minimal disturbance.

If you are able to trickle the water in, then the heater in the tank also has the chance to "take the chill off" while new water is introduced.

Id suggest no more than 3 degree temp drop for most fishies - it depends on what fish you have. My community guys are plenty happy with 3 degrees.

If you cant add water slowly, then why not add it in 2 or maybe 3 lots?

 

[Schmill]

Ok thanks, as said I wouldn't normally do a drastic water change like that, it's only because I am still cycling, needed to 'reset' the water, and also the gravel needed a damn good vac now some of the silt had settled.
On my 60L tank I use a bucket, and used to let that 'stand' to warm up to room temp. To be honest on that one I probably change more water than neccasary as the flow needed to make the gravel vac work properly usually takes 2 buckets of water out by the time I've finished 'hoovering'.

On the 300L tank I changed at the weekend I use a hose to empty it, (which incidently is REALLY slow, bearly fast enough to make the gravel vac lift the silt up the wide part of the tube , but it does save the floor and step ladder from buckets of sloshing water), and a hose to fill it. I could as you say 'trickle' the water in from the hose I guess but it all comes down to time I'm afriad. I'd be too worried to just 'leave' the tank filling from the hose, (even slowly!) so I ahve to watch the tank the whole time, (especially as I have 2 young boys who would think nothing of pulling the hose out of the tank and having a waterfight in the middle of the lounge I'm sure!). It's not too bad for the 10-15 minutes or so that it took, but if it needs to trickle in over an hour or 2 that sounds like a nightmare
I guess one option would be to 'overkill' on the heaters, such that during a top-up the water temperature might drop but would be returned to normal very quickly? (Hopefully quicker than it would take for the fish to shock or aclimatise to the low temperature)

 

[saz326]

I guess one option would be to 'overkill' on the heaters, such that during a top-up the water temperature might drop but would be returned to normal very quickly? (Hopefully quicker than it would take for the fish to shock or aclimatise to the low temperature)

You could certainly use a couple of extra heaters while topping up... good thinking. Sadly you cant just turn heaters up as the heat output is constant on most heaters, they dont heat water up more quickly if you turn them up higher - they simply reach a higher final temperature.

If you cant have a hose trickling in (im NOT talking really slow slow here) then how about having a tub on the top of the tank that you can fill from the hose and then let water from the tub trickle into the tank through a hole in the bottom?

When I do a big water change I put a big bucket on the tank, and fill it with cold water and dechlorinator. I then put a piece of airline hose from the bucket into the tank and allow the water to siphon out. I then top up the bucket with water if its needed. This way there are no hoses laying around for the boyfriend to trip over - clumsey man he is.

 

[kribensis12]

I dont bother with it too much. My tank is at 82 degree's, and i just take a bucket and fill it halfway with scolding hot, and then halfway with freezing cold. It seems to get the job done. My angels dont agrue with it.

 

[petertr]

Keep your water changes to 1/3 or less and there's nothing to worry about in filling with cold water.

 

[andywg]

Keep your water changes to 1/3 or less and there's nothing to worry about in filling with cold water.

^^ This ^^

It's correct.

 

[minxfishy]

Have you tried B+Q or garden centre for a tap adaptor to fit, I have a mixer tap, square kinda shape, awkward thing, but you can get different size adaptors that go over the top of the tap, then with different washers fit snugly onto the tap by screwing the adaptor up. Hoselock do lots of different ones.

Failing that, if you do want to do a 50% water change, just add some hot water to a bucket whilst filing from the hose and poor it in slowly as well, thus not making the temp drop too much.

 

[Schmill]

Have you tried B+Q or garden centre for a tap adaptor to fit, I have a mixer tap, square kinda shape, awkward thing, but you can get different size adaptors that go over the top of the tap, then with different washers fit snugly onto the tap by screwing the adaptor up. Hoselock do lots of different ones.

Failing that, if you do want to do a 50% water change, just add some hot water to a bucket whilst filing from the hose and poor it in slowly as well, thus not making the temp drop too much.

Yeah thanks, it's a pain to be honest. I spent however much on the fancy hoselock adaptor, that comes with the assortment of washers as you say, and then you screw-clamp it onto the tap. Not matter how I try to arrange it though, or how tight / loose I do the clamp I always get water squirting either out of the front or the rear of the adaptor
So in the end I ended up hauling the hose round the house to the hoselock connector on the cold mains tap outside - lol

Also, in case anyone knows, I'm guessing it's to do with fluid dynamics and drag, but my syphon of the dirty water from the tank is much slower when doing it connected to a length of hosepipe rather than holding the bucket and syphoning straight into that. As above, so slow that the gravel vac bearly works. Does anyone know of a small powered pump that can be used at either end of the hose pipe when syphoning the tank?

 

[minxfishy]

Yeah I have some trouble with the python if my mains water doesnt have enough pressure, but generally its ok. I often dont get the connection right on the tap and have squirting water, I just lay a towel over the tap too lazy to take it back off and refix it