Thanks for your response Amanda.
He was given a clean bill of health, no giardia or anything else. He had 3 stool tests done just to rule anything out. My vet said that the original case of diarrhea was probably due to the stress of moving (I recently relocated). And she also said that the occasional loose stool he has is nothing to worry about, unless it gets to be more consistent like before. It's pretty infrequent when they are looser, but even when they are, they're not runny.