I've installed half a dozen shrimp in my tank to help with cleanup. They’re doing an excellent job of cleaning the bogwood but don’t much like green algae for some reason. The bogwood’s going to be pretty clean soon so I thought I best offer them something else. I bought some Algae wafers from the LFS and placed then in a shallow glass container and they haven’t touched it. Several of them had a sniff but then wandered off without eating anything. Are there any particular foods shrimp like?