Thanks for you advice !
The thing is that I already bought this tank, it's not very cheap so I'd like to keep them in it for the moment. When they grow up, I'm planning to move one of them in another 55 gallon tank.

The guy at the pet store said they'd be fine together, and I think he's right, they always stay in the same hide without any conflict.

So if they can't be in a separate enclosure, what would you say about how to feed them ?