I thought the crab was big enough to be safe, at least for now but the eel was on it within a couple minutes. I don't know how it survived that attack to be honest.
Oh and as the hermit grows he has to find a new shell, not too big not too small, and with 4 eels in the tank I'll go out on a limb and say his time is imminent. Just on a side note, many that keep hermits fail to supply various shells for their hermits to relocate, they can't survive long outside of a shell.