I'm trying to get my frog, Bonk checked out, but he always either poops in the water dish, or has a very tiny watery smear.

Does anyone know how big the sample would need to be in order to get properly checked out? Can labs do analysis based only on a tiny smear on a paper towel?

Also, the vet's asked that the sample be fresh. Since it takes about thirty minutes to get to the vet's I'm assuming I'd have to leave as soon as I spotted the poop unless refrigeration would help. Can refrigeration help? How long can it be left and still be fresh?

I've almost considered leaving the water dish out of the tank for a night and just misting the tank well, but that sounds dangerous. I'm pretty sure this frog has some kind of problem, given the runny poop and I'd like to get him treated as soon as possible, but it's really frustrating me.