depends on what you want to clean. I find the emerald crab is great for cleaning rocks and glass he can reach from all sorts of algae. You'd have to clean the glass yourself and probably get some sort of snail just to help out a bit. 29 gal can probably support one Mexican turbo snail, which is supposed to be very hard working. its an absolute tank though. the turbo and the emerald will throw coral frags around so make sure you glue any frags into place securely.
The emerald will also take care of most uneaten food. its a good all round CUC member, but remember to keep him well fed if the rocks are already all clean from algae.
shrimp are useful for uneaten food, but the emerald crab already does that. if you run into an aiptasia problem in the future, a peppermint shrimp might be useful, but again keep that one well fed.
you may also want to invest in one hermit crab just for added algae coverage and additional scavenging force. one is usually best if you already have the turbo and the emerald. more crabs and they'll fight for snail shells. either way provide a lot of shells for the hermit. stick to "reef-safe", dwarf hermits although the electric blue hermit might be reef safe as well. he grows bigger though.