I don't think that mixing your species together would be a good idea- as I'm not sure of the different diseases or toxins that each frog carries. Also, White's Tree Frogs will pretty much eat anything that wiggles, and is big enough to fit in their mouths. If your gray were to be smaller than your White's you could wake up one morning and find that your Gray had 'mysteriously' disappeared. Lovely little guy though! I'm waiting on my two new White's to acclimate and get comfortable, as well. It takes a lot of patience. No two frogs are alike. My first White's was comfortable almost immediately. He was up and around in no time. And these two- they're very shy right now and like to hide. They'll come out eventually. Congrats on the new froggy! They are addicting!