Could you please Id this critter from beach sand?

[KSean]

Brought a handful of ocean sand to seed my new small 5 Gallon tank. Intentional. Wanted to experiment in a small tank with ocean sand/seeding.
Saw these guys running around. Does anyone know what these are?
I am planning to set up the tank as an exclusive nem tank. So in essence they will be living with a couple of BTAs. Will that be an issue?
FWIW, they are from California beach.

 

[tbrown]

I always called them Sand Fleas. Not sure if that's their actual name...

 

[KSean]

Thank you. will read up on them. they are quite active swimming around in the tank!

 

[Hubert J. Farnsworth]

also commonly called mole crabs

 

[old salt reefer]

I used to bring them home for my triggerfish to eat, he loved them.

 

[Townes_Van_Camp]

Sand fleas, big ole pods I do believe. Great fishing bait. I've bought them at bait stores here in Jacksonville to add to my tank. They never harm anything. They are detritus eaters as far as I know. They also don't ever live long in my tanks. I'm not sure if they can live submerged forever. But I've never seen one out of the water. I've only seen them in intertidal areas, spillways, beaches,.etc.

 

[EricR]

Being from Southern California, we always called 'em "sand crabs",,, but I'm old.
I see "sand flea" used a lot now.
*both of those options are obviously just common terms and not scientific