How can I perform a successful water change?

[J.Mcpeak]

Wow thanks for the replies everyone! I will definitely turn my heater off now; can't risk killing any of my fish. So about using cooler water .. What about this can trigger breeding in tropical fish ? I am certainly going to give "cool rain" a try.

This works on some fish. Some fish it is a slower turn over, some fish come in from the sea so a SG change is necessary B. Doriae for example, they are all different. Research the species you wish to breed as some aren't so good with the fluctuation, corydoras it's a sudden drop to 17C' my clown loach would go into spasm at that temp, I know I've done it! Some fish just "do it" without any assistance.