I'm in need of some information on how to do this. I currently have 5 longtail zebra danio's in my community tank, the tank is heated and stays between 75 - 77 degree's at all times. I would like to move them into my 35 gal goldfish tank (fully cycled) (which only has two fancy goldfish, and plenty of filtration to handle the new fish) My goldfish tank is not heated, and usually maintains a temperature of between 65 - 69 degree's. I was considering doing one of three things... 1) On my next water change add warmer water to the goldfish tank to increase the temperature to around 70 - 72 degrees, add the danios, and than let the temperature even out again to it's normal 65 - 69 degrees over the next few days so it's not a dramatic change... 2) Drop the temperature by a few degree's on my community tank, maybe down to 72 degrees and than add them to the goldfish tank. 3) Add a heater for a short period of time to the goldfish tank until the water reaches around 74-75 degrees and than put the danios in and slowly reduce the temperature until it reaches it's normal 65-69 degrees before removing it... any suggestions about if this is the right way to go about doing this. I don't want to shock my fish by sudden temperature changes.