You also have to take your biological load into account. Even if you keep a pair of ocellaris or percula clownfish (the two smallest species), the females can get to be about 3" long. With that in mind, I would keep just one more small fish in a 29G--maybe a shrimp goby or a firefish--if you keep ocellaris or perculas. I probably wouldn't keep bigger species like Clark's or tomatoes in a tank that size.