Can it be done? Yes. Should it? Probably not.
Owning pets requires you to be careful and responsible. That means ensuring your critters are safe. Housing them separetely will give them a better chance of a stress free life. Keep them separate until you have sexed them (AT LEAST!) to ensure...
I have seen many on these forums who recommend a minimum of a 20 gallon tank for a pair of adult cresties. Unless you want to breed the little guys, it is not recommended to keep them in the same cage. Be sure that they are within a couple grams of each other size wise, otherwise problems could...