As was mentioned by Scottyhorse, your tank is not mature enough for bamboo shrimp. They feed off microbes that colonize mature filter media, and fan it out off the current.
If you can't rehome it, your best bet is to supplement it's diet with crushed up algae wafers etc. Just google supplementally feeding bamboo shrimp ... If you haven't already. A good filter with flow like an HOB or canister should provide the necessary flow.