Will you need a heater in your aquarium? Well that depends on where you
live, where the tank will be and what type of fish you will be keeping.
First you need to find out what temperature your fish are most comfortable
in. Goldfish and white cloud minnows like cooler water temperatures at
about 18 to 21 degrees Celsius, or 64 to 70 degrees F. Other fish like
warmer waters from 23 to 27 C (74 to 82 F). When you buy a fish the store
keepers will be able to tell you what temperature is best for them.
So now you know what temperature your fish want. The question is if you
have an aquarium of water left sitting out without a heater, what
temperature will the water be? Usually is will be a few degrees below
room temperature. If the aquarium is in direct sunlight the water may
warm up a little. However, if it has direct sunlight algae will grow in
it and become a problem.
It is a good idea to let a new aquarium sit a few days before adding fish.
If you do not know if a heater is needed because you live in a warm
environment you can use this time to test the water temperature and see if
you need to add a heater.