Dwarf shrimp would be fine in that tank, the most commonly available being red cherry shrimp. These are also the easiest to care for and a good beginner shrimp.
Amano's are great, they also don't breed where if Cherry's get the chance will breed quite a bit. (Though, i'm guessing bigger fish would eat the offspring).
They are omivores, algae eaters naturally I believe. They like to feed on the 'biofilm' that is present in all aquariums. I just feed mine powdered flake food, algae tablets, blanched veg. You can buy specialist food, but to be honest mine are breeding and happy with what they get. Though feed sparingly, too much food pollutes the water and shrimp are senstivie.