Hi sneed,
I've been told several different things regarding the number of inverts in a tank. One LFS told me 1 snail and 1 hermit crab for every gallon! And another told me 1 snail for every gallon and 1 crab for every 5 gallons! Of course, LFS are not always reliable. But I've had some people tell me about 25 snails for a 50 was a good amount and it was suggested to me to get 25 hermits also.
So my point is- everybody is different- I think it's a matter of opinion. I'm sure it also depends on whether you have LR or not. The snails and crabs are always picking off the LR as well as LS and glass.
I have 25 snails in my 50. About 8 of them are fairly big, and the rest range from nickel size to smaller than dimes. I have 10 hermits- 5 red legged and 5 regular... Everyone seems to be happy. They keep they tank clean, but they all seem to have enough to eat.
But I am still new to this hobby also, so maybe someone else will give more feedback.
Good luck!