How often and how much do I feed guppies?

I constantly hear different answers about this. that's why I'm so rather confused. At the moment I feed my 8 male guppies in my planted 10 gallon 3 times a week. The rest of the time they are grazing on the biofilm of my Amazon sword plants. Is this a good routine, or should I feed them once a day? Generally confused on this topic. Thanks for your help.