Many thanks to Doctor Foster and Smith
the heater I was using, All Glass now known as Aqueon (grrrr) in my guppy tank, set at 80 degrees, but the water was 90 degrees. Turned it down, and down, and down to 70, and the water is just now at 80 degrees. I would never buy anything from Aqueon, my husband worked there for awhile, management is terrible, they treat their employees like crap! That's all I have to say.
Bought a new heater from Doctors Foster and Smith, my order was delivered in one day. I'm happy was well as my guppies are happy. That makes for a wonderful day.