Well Ok maybe hundreds.
I collect fiddler crabs for food for my burfish and also because they are just interesting.
Occasionally, like today, they spawn and I am burried in tiny fiddler crab fry.
At birth they are a little larger then baby brine shrimp and are born alive.
The female keeps the eggs under her belly for a week or two then releases them when they hatch.
I have them in a seperate tank but I strained out a few dozen for my reef where they will be coral food.
They will not reach adulthood as these things have been spawning in there for decades and I have yet to find an adult in my tank.
They are not really true sub marine crabs and spend half of their time out of the water when the tide goes out. I collect them on the edges of tide pools when the tide goes out and they are very common

Fiddler crabs are great, as a kid living on the coast in Virginia we would catch them for bait.

__________________
Freedom is not free, support the troops.
U.S. Marine Corps, U.S. Army retired. 27 Years total.

110 Gallon FOWLR with sump and refugium.
1 Dog Faced Puffer, 3 Blue Damsels, 2 Maroon Clowns, 2 Ocellaris Clowns, 1 Blue Tang, 1 Coral Beauty and 1 Convict Goby. Lots of snails and crabs.
Deep Sand Bed and 75 Lbs of Live Rock (how do I know the weight of the rock? I used the SWAG system. If you don't know what that is PM me and I will explain)

Today I collected a bunch more with hermits, snails andf pipefish.
I am still a kid at heart.