Interesting question. Lets assume, just for the sake of argument, that the activated carbon does remove the pheromone efficiently from the water. (I don't know, but it might be true.)
Then lets assume that newts normally breed in large bodies of water. Even a small breeding pool may be orders of magnitude larger than our aquariums. And some tail-fanners even breed in slow-moving streams, where their pheromones are quickly washed away. In either case, the concentration of pheromone in the surrounding water would reach near-zero very quickly.
My conclusion would be that the situation in the filtered aquarium is about the same as in the wild. All the pheromone that drifts away from the immediate scene of courtship "disappears", either by being filtered out or by being diluted to the point of non-existence.
It seems likely to me that what matters is the concentration of pheromone right in the immediate vicinity of the tail fanning activity. If the male fails to impress the female with the pheromone he waves directly into her face, he's not going to have any better luck with small residual amounts that might linger in the aquarium water.
So I doubt that carbon filtration would affect breeding.
[
Note added: I just realized that my post is basically the same point as Nathan's. Either his post wasn't there when I started writing, or I just hadn't read it.]