As a general rule you can have one pair of any species (i.e. Percula or Ocellaris), color doesn't matter. You could have a normal clownfish with a black clownfish with no problem, as long as they're the same species. Having more than one pair of clownfish is a recipe for disaster. I tried it in a 300 gallon tank with no success, and there are multiple hiding places/hosts. You could get lucky, but its not worth it.