In my (almost)dedicated shrimp tanks that are soil based heavy planted....I feed mine-half an algae wafer and some of my homemade food every other day and a large pinch of Ocean nutrition community formula flake food daily-this is for the shrimp, snails and the plants (flake food is a great plant food too) I also leave all the exoskeleton they shed so they can eat them and what they don't eat the snails will and/or breakdown for the plants.
I like to keep an (almost) shrimp only tanks (5-10gal) so that I can seed my other tank from it-That way I will always have a healthy colony of shrimp without worrying about them all being eaten or killed. However, sometimes I will use my shrimp only tanks on occasion to spawn and leave the fry in for a few weeks before I move the fry to grow out tanks. The breeders will eat some of the shrimplets, but never enough to make an impact on the colony-since the breeders may not be in that tank for longer than a few days anyway-Plus, I have lots of cover in the way of java moss.
I can't prove this, but in my tanks- it seems if the Bettas are raised with shrimp-they don't seem to harass the adult shrimp as much-they do eat any shrimplets small enough to fit in their mouths-but that is to be expected since they would be considered part of the Betta natural diet.