Goldfish are one thing, but trying to move the new cat in with the old dog, or vice versa? That is a little bit like how your kids are getting along, huh? Fighting like cats and dogs!!! Hardy har, har, har. Not funny at all! Depending on the breed & socialization of a dog, canines really like, and have a healthy respect for cats. Some terrier breeds are notorious for having a "taste" for cats, so you will have to take that into account! If the dog likes to chase cats (what dog doesn't?), make sure it knows that is NOT allowed through words and tone. EVERY time it tries to chase. Cats however, are totally different animals. They don't tend to change home situations easily, and they don't often integrate easily into a house with another cat. Sad, but true. One thing you have to do is keep the cat indoors at the new house for a minimum of three days to let it know this is where you want it to stay. Another thing you should do is put your scent (cologne or perfume) on the new dog or cat, and on as many surfaces that the cat will come in contact with before he or she moves into the new house. A cat's olfactory sense is very keen, and your scent is familiar and comforting to him or her. Avoiding jealousy between animals is just like kids: pay an equal amount of attention to them. Keep all of the dog rules for all dogs, and all of the cat rules for all cats. Of course, feeding times should be consistent and they should all have their own feeding places established safely, fairly, and right away.