Definitely macro algae as others have said. Your tank parameters are pretty good, salinity is on the high side, but not out of normal.
I like some macro algae in my tanks, as long as it stays in check, I think yours looks pretty sweet. I've had similar, if not the same. Never had it grower very far for me, but that's variable. I've never bred clowns, but my understanding is if their inclined to mate you would be hard pressed to stop them.
I think the fry would use the macro algae, but just a guess. Keep us posted...
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