For what it's worth, there's a LFS about an hour away from me that has a pair of chrysopterus. From what I've seen of those two, a 30 wouldn't be enough space. These are very big, deep-bodied, robust fish that are also quite active. The female is almost as long as my hand (and I'm almost 5'9"). Scott Michael also says (and I can confirm this from the pair of Clark's that I kept) that clowns in the clarkii complex tend to roam away from their hosts a lot more often and a lot farther than other clownfish species--probably because they're better swimmers. The male of this particular pair of chrysopterus tends to stay near their end of the tank and their anemone, but the female roams all over (and terrorizes!) the entire 700G tank.