Wow that is a lot of hermit crabs! I guess it all depends on how much alage you have. I have heard 1 per gallon, but that seem like a good start.
It will be the thunder dome when they all start needing new shells [emoji23]
I'll only have the scarlet reef hermits in my systems. I currently have 1. It's someplace around 25 years old I think. At least I got it before I got married in 2001. The others all tend to be a little too opportunistic when it comes to feeding time.