tank change from cold to heated water

[shadowkeeper21]

I recently brought some platys from my local fish shop and was told they where told that they where coldwater fish. I went to a proper fish shop and was told they need heated water. I plan on moving my fish from my old tank to my new bigger tank, and was just wondering how to transfer them over.

 

[StevenF]

the first thing you need to do is to properly cycle your new tank according to these instructionshttp/www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/

I would recommend that you complete the cycle before installing any live plants (if you want live plants). Note you will need a water test kit. Preferably one that measures Ammonia, nitrite, nitrate, PH (Acidity, GH (general hardness), and KH (Total Alkalinity. If you have any parasites or sick fish in the old tank you should address those issues now. Otherwise you could move the parasites and disease to the new tank.

While that is going on you can install and adjust your heater and adjust it. to the desired temperature which is commonly 78F.

Once the tank is cycled, heater and any other final preparations are done check your water in both tanks. Ideally you want Ammonia, and nitrite at zero,Nitrate less than 20 PH between 6.5 and 8 (ideally 7), and your GH and KH in both tanks to match. If they don't match you can slowly over a day transfer water slowly between the too tanks to get the water to match. Do not move large amounts of water all at once. Moving 1 gallon about one per hour should be safe for the fish. Doing it more quickly could shock or kill the fish. This will also help slowly bring the temperature of the cold tank to the new temperature. Again you want the two tanks at about the same temperature. Once the temperature and all the water parameters match you can move your fish over to the new tank.

 

[eaglesaquarium]

While that is going on you can install and adjust your heater and adjust it. to the desired temperature which is commonly 78F.

That is quite on the high side. Anywhere 72-75 would be plenty warm enough.
http://www.seriouslyfish.com/species/xiphophorus-maculatus/
(Considered 68-79 as the acceptable range.)

Higher temps also increases the metabolism of the fish, increasing waste and potentially shortening the life span.