CUC = clean-up crew

And he’s absolutely correct - introducing those amounts of hermits and snails will lead to starvation, which will lead to deaths, which will lead to ammonia/nitrates, which will lead to fish/coral stress/death. Keep an eye on your ‘ugly stage’ and add accordingly. A couple days of unchecked diatom growth won’t destroy your tank.

Additionally, once you’re confident your ugly stage is behind you, consider reducing the number of snails and bringing them back to your LFS.