Originally Posted by NigelN

Hi bro, the white one is most probably a P. Clarkii. It's claws and head is 'rough' in texture, while the Blue Moon has smooth surfaces all over. Also, the Clarkii has longer and sharper-looking pincers while the Blue Moon has fatter/more stout claws with shorter tips. The Clarkii looks like it can cut, the Blue Moon looks like it can crush. Well most probably they are fighting for space. Cherax species quite peaceful but Clarkiis are damn aggressive and rarely peaceful.

Keeping them both are possible, but you must give each of them a hiding place (best to have 3 available). Also, do you have plants? I notice that my Clarkiis like to 'hang out' (literally) in plants, climbing to the surface to breathe air at times, while the Blue Moon (and other Cherax species) stay at the bottom and 'shake leg'. BTW I have a mix of 2 Clarkiis, 3 Cherax species in my tank: 2 P. Clarkii red, 2 Blue Moon, 3 Zebra (Cherax Peknyi) and 1 Australian red-claw lobster.

Oh did you check to see if your Blue Moon is a male? My male was a bit aggressive when he went into the tank. Then after a while he was peaceful and allowed another Zebra to climb on top of him. :P