On the other hand, get them to isolated and they die off before mating. Spotted fish are rather aggressive in that they eat any plain fish smaller than them. They go through food at a reasonable rate and thus can multiply faster than the clown fish population.
Plain fish are sort of the bottom fodder in that they just eat fish food, no other fish.
They also have the tendency to reproduce like bunny rabbits. Basically the community goes really well until around step 515, then within 10 steps, the population dies out except for a few random spotted fish, which die soon after. Another interesting setting is 1000 steps, if you set each fish type at 10 and keep the food settings as above. This is interesting since its very unstable, sometimes the spotted ones take over the tank, other times there are large plain fish or lots of little fish.