Thought I'd Killed Him :(

[Schmill]

So yesterday I decided to do the waterchange on my 60L tank, to get around with the gravel vac I usually take out around 20L of water, which is 2 buckets full.
So I did the vac & chucked the old water, put fresh water into the buckets with dechlor and then cleaned the condensation cover, tidied plants etc. Once everything was done I refilled the tank with the two buckets of freshwater, put the tank back together and checked on everyone.
One of my male dwarf rainbow fish was flicking a bit against various things, and the other one was in a really bad way, sometimes nose down, othertimes completely upside down, sometimes on his side, before finally finding somewhere to prop himself up.
I wasn't sure what had happened and at first presumed that he must have swum into the flow of water from the bucket and been pounded against something
Then I noticed the condensation starting to form on the outside of the tank and rushed to check the thermometer, 16 deg C ! As I normally keep the water around 24 deg C it must have dropped 8 degrees in about 1 minute that it took me to empty the buckets.

After trying to net the rainbows so that Icould 'contain them' in the water above the heater, (and failing miserably), I syphoned 10L of the water back out again, dumped half of it, and furiously boiled the kettle and microwaved jugs of water, getting the bucket up to about 32 deg C (according to the tank thermometer), and then slowly poured that back into the tank.
That seemed to bring the water back to around 24 deg C nicely, and the effect on the rainbows was obvious, one was immediately better, the other (that had been the worst) was at least able to start swimming properly again, and swam to the top of the tank and sat in the filter flow for a while.

I've also put a dose of Melafix into the tank now 'just in case' due to the aggitated movements of both the male rainbows when they were cold against the substrate and decor. Surprisingly enough the female never seemed effected!

All in all, this morning everyone seems fine and happy so I think (fingers crossed), I got away with it.
Is there anything else I should do?

Also a warning to other people in this cold weather, keep an eye on the tank 'stat when you do your water changes - lol

 

[Athena]

Yes, I noticed the same thing this weekend when I was doing water changes, especially as I had decided to do a thorough gravel clean, glass scrape, filter clean, plant tidy-up etc on one particular tank. It all takes time and I don't like doing any maintenance work with the power on.

Within a very short amount of time I noticed the tank water temp had dropped quite a bit, so had to work like Speedy Gonzalez to get the tank topped up etc. Thankfully, at my house I have a new combi boiler - which means the water comes direct from the cold mains, so water from the hot or cold taps is from the same source. It means I am able to use water from the hot tap to add to cold water when doing water changes, to get it to the right temp.

I didn't want to stress the fish with temps going up and down like crazy, so rather than add water back at the higher temp, I made it slightly lower temp than normal (but obviously a few degrees warmer than what was in the tank) - added it and turned the heater thermostat back on. Didn't take long to go back up to 28 degrees and all the fishies were fine and no ill-effects.

I don't think I will do a major clean-up job on a tank during severe cold weather spells in future! Even with my central heating on, my house is not that warm to be honest (probably cos I have wooden floors and not carpet).

I just didn't realise how quickly water temps can reduce once that thermostat is turned off.

Athena

 

[minxfishy]

My tanks during water changes have been dropping more in temp over the last few weeks too, due to the cold water direct from the tap being much colder than normal during this freezing weather, so Ive been using hot and cold mixed and will continue to do so until it warms up a bit.

 

[Schmill]

Unfortunately my hot water system is one that uses a large water storage tank in the loft and then a large copper 'hot tank' for heating the water in, so I am very nervous about what copper might get in my tank if I use hot tap water. API have said that the dechlor will deal with copper, but I don't want to risk it.
I think when I come to do the water change on the 300L tank though the kettle might be getting a LOT of use!