What temp to breed guppies?

anywhere above freezing, and below boiling. Just kidding. Mine have breed in everything from 72 to 82. Not sure on optimal temp though.
 
mine breed the best at around 80 degrees.
i have had guppies in tanks without a heater and the female would get pregnant but I never saw any fry. dont know if the mom had them and ate them or what...
whereas in the warmer tank, i'd have lots of fry.
 
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