Converting From Tropical To Coldwater?

[johnringham]

I have a 260l tank that I'd like to convert to cold water. Is there anything I need to consider please?

Thanks
John

 

[techen]

Loose the heater and keep the filter. Note that goldfish need quite huge tanks though

 

[Lunar Jetman]

Yep, as above. Lose the heater, keep everything else and lower your expectations with regards to the number of fish you can keep!

 

[TallTree01]

Wouldn't it be more because there's more oxygen in the water?
Unless you speak of goldfish in which case you're spot on.

 

[fluttermoth]

Wouldn't it be more because there's more oxygen in the water?

You'd think that, but the actual difference in oxygen levels is minimal.
 
The most important factor with stocking in coldwater v tropical, is the difference in efficiency of the filter bacteria. They work less efficiently in colder water (which is, of course, why we turned the temperature up in fishless cycles) and so can't cope with the same levels of waste. That's really the limiting factor.

 

[PrairieSunflower]

Interesting Fluttermouth... must be why coldwater fish were such a disaster for me when I started out.  Tropical has been so much easier.

 

[goldfinger]

Goldfish poo is the devil's snacks, its like a mini with clowns that keep coming out!
I find goldfish much better to look at IMO. My new rule is when buying a filter instead of doubling the output tripple it or even quad it a bigger filter is your friend!

 

[fluttermoth]

I must say, I do find goldies a bit dull to look at; they don't have the range of colours, especially that bright metallic blue, that tropicals have.
 
They are lovely characters though; one the most favourite fish I ever knew was a little calico fantail, called Flounder, that my friend had dumped on her doorstep. He was just such a sweet little guy. I cried buckets when he passed on, and he wasn't even mine!

 

[goldfinger]

Its always sad to see a goldfish go up to the big sky tank!
For me watching the fins and fan tails swishing in a tank peacefull and tropical fish dart too fast depends upon fishes, but the colour of goldfish seem real and more natrual My next purchase will be a black Ranchu and a pearlscale or even a panda silver and black saw one with black lips looked stunning!

 

[johnringham]

Can I just ditch the heater and do a partial water change or do I need to start again please?

 

[fluttermoth]

You can just ditch the heater.
 
Don't forget you'll need to re-stock within a day or two of moving your tropical fish (or feed your filter with fish food or ammonia) or your filter bacteria will die off, and you'd have to cycle the tank again.