Thank you guys so much! It is so nice to wake up to all these helpful comments.

I think I'm going to bring him to a vet once I get the second White's Tree Frog at the Reptile Expo, this way I don't have to go through stressing out these poor frogs twice. I took him out for a minute last night to get a closer look at the vein thing, it's kind of puffy...looks almost like it was a cut that healed? Could be a scar? It's definitely not a piece of debris. He also chirped when I picked him up. The second I touched his scar, though, he "peed"...so I felt really bad stressing him out so much. But then that worried me because he was okay if I touched other parts of him, but touching that spot caused him to shoot that water out of his butt. Hahaha, I admit it shocked me...even though I knew that at one point he would probably do that...Anywho! I definitely want to get it checked just in case.

The tank they had him in at the pet store was very tiny, not very tall or wide. It was lined with papertowel, had a stick in the middle and then a clump of moss on the side. I guess the reason he was so light and bright green is because his environment was very light. I have him in an 18x18x24 Exo-terra terrarium with coconut fiber substrate, some flat moss on top of that, and then I have a little bit of that looser moss on the sides. I have a couple of real plants and then I have those fake ones with the suction cups on the sides. I think it's super pretty and I hope he's enjoying it at night when I am sound asleep.

1beataway, to answer your questions: I am actually sitting next to his terrarium right now. I've seen him physically eat about 4 crickets so far and this is because he attacks them right away as soon as I let them loose inside the habitat. As of last night, he's eaten three more crickets. I put them in there before I went to sleep and..well...they're gone. I have seen/taken out...2 pieces of poo, but the others could be somewhere in the moss that I can't see. And he is definitely using his water dish...I filled it to the top last night and cleaned it out good. Right now, it's all dirty and the water is nearly all gone.

Okay. I'm feeling a bit better about this. Do you guys think adding another little guy this week is okay or do you feel I should check out the vein on his back first in case it is some sort of parasite? Thanks to IgbyKibbits, Kurt, and Crystal6 for your input. I appreciate the help so much!