I find 68f-70f is the best temp- for them guppy's are less except-able to diseases when kept at low temps most people keeping guppies at higher temps seem to have more problems then when kept at a lower temps
lower temps are far better i have never kept any guppies above 74 and have never had any problems with them.
Tips
Temperature, keep them at about 74f – degrees
Water changes
40%-50% once a week or 2 weeks never change more then 50% at any one time .
Fry I find it best to do a water changes of 10%-20% for the first 3 weeks
Feeding,
guppies will except all flake food.s frozen blood worms.are good for them.
It is best to add some live foods in there diet .
Fry crushed flake it is best to start them on live foods like baby brine shrimp
/ microworm