Also guppies like to have a bit of salt in the water, upto 1 tsp per 4.5ltrs.
Not everyone does this, it's a personal choice.
Try to have two females to one male, sometimes if you only got males they will start fighting. Or if too few females, the females never get a break.
I have been told guppies like the Ph around 7.2.
Have lots of plants and things in the tank, so if any do want some time out they can find some place to hide. Some guppies do like sleepong and sword plants at night.