I agree with whats been said, a 4x2x2 is minimum for an adult beardie, my beardie is small for an adult but hes in a 4x2x2 and i really cudnt imagine him being in anything smaller. the puffed beard i wudnt worry about aslong as its not black which wud mean its stressed, mine puffs his beard out from time to time when hes chilling on his log.