To answer the question about hermits propagating......
I don't think your hermits are reproducing. They may spawn and hatch, but I believe you need a tremendous
amount of phytoplankton available to them in order to get them to settle out and that could take a lot of time.
They'd most likely be eaten by fish or corals or they'd end up as skimmate if you are using a protein skimmer.
I personally like a cleanup crew that self propagates so I don't have to repopulate them every few months. I use
stomatellas, columbellids, colonistas, and direct developing nassarius. I wish I had some ceriths that are known
to propagate in reef tanks. About the only cleanup crew I buy are cucumbers, urchins, emerald crabs, and if I can
find them, money cowries.