how many crabs can one have in an 80g "cube"

[reef tank 2.0]

im a month into my cycle, so still waiting for that to finish....

in the mean time, I am still window shopping for livestock.
when the time comes for crabs, (non hermit), how many can be in an 80g cube?
with my tank being 30x24, is there a chance they would end up fighting?

I am not sure which ones I want. I used to have a serpent sea star in my last tank, I'd like to get one of those again. I'd like to get an urchin of some type later down the road too. I need to keep that in mind to make sure they'd all play well.

I'm not looking to get a bunch of the crabs, just wanna know options.

I've always been iffy about the emerald crabs, too many stories about eating corals.
definitely have my eyes on the pom poms and porcelain.

(i think I need to learn how to branch out and try different species of livestock. I had a number of fish in my last tank, which I really liked. I'm wanting to get a few of them again. But I'm also in a smaller tank, and limited on water volume. So the amount of fish I can get is a lot less. So I have to choose wisely, for both Inverts and fish)

 

[coralboi56]

You can get pom pom crabs, but keep in mind they will get lost in that large of a tank. I have one in my 7.4g and the only reason I can see him is because I know what crevice in the rockscape he calls home. He rarely ever comes out from it.

I've never had a problem with emerald crabs personally.

 

[The_Paradox]

If you get emeralds just stick to females. Over the years every male around age 1-2 started giving me problems and ended up sump monsters. I have a couple females coming up on 3 and they still behave.