Bamboo shrimp can be fed a number of things. Best is liquid cultured single cell algae, or Golden Pearls in the 5-50 micron size, Liquid Phyto plankton sold to feed corals, even baker's yeast dissolved in water first, frozen oyster eggs, live micro or banana worms or other tiny crustaceans. Two Little Fishies makes a spray dried algae feed and spray dried crustacean meal, both are very good, but costly. Spirulina powder mixed in water is good too. Hard to mix, I put a tsp in a jar, put on a tight lid and shake hard for a few minutes.
Feed one or more of these foods at least a few times a week and make sure there is enough water current so they can fan feed in it. A perch in front of the water flow is ideal, and if you can turn off the filter for awhile after feeding, but keep the water circulating with a pump, it helps them get the most from their food.