It has been said that a 2 degree shift will signal them to span. Goldfish seem to benefit from a seasonal temperature change. Do not panick if your fish are exposed to higher temperatures as they can weather them so long as there is sufficent oxygen in the water. Do not expect fish in crowded tanks to do well in warm weather. All transition should be gradual.
Water quality is important.
When you first set up a tank you will need to daily tests of amonia and nitrate levels to monitor the cycling of the bio filter. After the tank has cycled a regular maintance schedule should be followed to ensure that the water quality remains good. Doing so may disturb the slime coat and lead to problems such as ich, velvet, or fungus. Instead do what he pros do. This may take a little getting used to but after a while it becomes natural.