I have seen mixed species host and there are examples of breeding (maroon and ocellaris are an example of two fish from different genuses, Premnas and Amphiprion) that are able to bond and reproduce, but I have read that it can lead to reduced vitality and vigor. Although a A. Clarkii and A. frenatus are both Amphiprion, they are from different complexes and you *may* have fertilization issues or larval vigor issues, and full grown fish may not grow and develop quite right. If its something you are interested in trying to breed, I would think long and hard about it simply because you are mixing species, and then spreading those fish out to others. But as long as the fish get along and you like the way the look together and interact together, then leave them be and see what happens before you worry about raising any potential larvae. It may take years before they spawn, and it's possible they never will.
I personally have not seen this particular mix of clowns, and I can't remember reading about them either, but there has been more mixing of clownfish species in the last few years, so I wouldn't be surprised if its been tried or done. Perhaps someone who has direct experience with it will chime in.
