Personally, I would not go adding anymore CUC members along with your new fish. I would keep a close eye on how the algae and organisms of the sort react, when you introduce the new fish. If you add more members to the CUC, not only will they contribute to the bio-load but the new fish will contribute as well. Which might cause a spike that the CUC can't handle, thus it will require more attention. I would supplement feed them. Maybe, a algae wafer or two? Possible pieces of seaweed to consume? When you add the new fish it may naturally create more food to balance everything out. I would work in increments, there are also places (like in between rocks) where we can't see nuisance algae growing, that these organisms can find.
Side note: Make sure that there are enough available shells for the hermits, you do not want a shell war on your hands!
