Your wife sounds like my husband (that I've seperated from). In marriage compromise is essential. If your wife is helping to take care of your tank, cats and lizards then I can see why she would say that. If it were me I'd keep the tank. Dogs are expensive to board or stay in hotel (added fees) when you go on vacation, plus training, feeding, walking, etc.
In my marriage I take care of my 90g, QTs, cat and dog. When I had surgery my husband wouldn't even medicate my QT that a new sick clown was in, or feed it, or top off water. Needless to say he was dead by the time I was released from the hospital (not what you want to come home to after having a huge tumor removed!) So in my situation I'd throw up the middle finger to that ultimatum.