" wrote:

I don't use heaters except in a Discus. Slows plant growth down also.
Regards,
Tom Barr

That comment probably needs qualification. I'm in California, and even here an
unheated tank runs aroung 66-68F during the winter, possibly colder at night if
its a small tank. An awful lot of fish are going to have trouble below 70F.

During the summer, of course, the heaters seldom turn on.