honestly, i would wait on adding a third frog until you have a bigger tank. unless you get one close to the same size, you are going to need to rear it a bit to get it bigger before adding it in with the established frogs. the tank you currently have could be used for that. if you set up the new tank, then move the pair, you free up the current tank to rear the new one in until it is large enough to join the other 2. if you get one the same size, then they should be in a bigger tank.

digital ones are much more accurate. you just need to be mindful of the probe. if it gets water in it, it can send the readings out of whack. but they are indeed much more accurate than the cheapo analog ones they sell at the stores.

white's are full of character. i did enjoy having them. no frog has made me laugh more, but also, no frog has driven me nuts like they did either. especially my male. he kept me up all hours of the night and he was 2 floors away from me. LOL