I have 5 in a 20g tall. The only aggression I've seen is one will raise claws and walk up to another and the other turns and walks away. FAR different from what is in some care sheets.
From what I have read, they can be considered much like bettas. Supposedly males are territorial and will fight in too small an enclosure. Basically a large amount of fems can be kept together with one male if desired. if the females fight, the male breaks it up and that's it.
As said though, it appears most of what I've read are people speculating or repeating sources. I haven't seen any true fighting at all. Maybe time will tell?
Also people seem to give params all over the place. So I've had to experiment with what seems to work for me.
Remin RO to GH 6 and PH 8+. TDS under 200. Seems to work for now. Time will tell if I need to adjust or if I have problems.
They are SUPER curious. They'll walk up to the tank glass when I go by it and will even eat out of the hand (or so I've read.) Their pincers don't hurt at all.