Long fin Albino Bristlenose, by the looks of things.
That's a combination of the genes of these two:
Longfin Bristlenose
and
Albino Bristlenose
First time I've seen a picture of that combination. I think Jools would like to have a copy under the "long fin" version to show the albino variety.
Lots of fish have genes for albinism and for long fins, so it's just a question of sufficient [in]breeding, and they'll happen. Obviously, both genes are rare in nature, as it's rather detrimental to the fish to be white or have extra long fins, when trying to hide and/or escape from a predator.
--
Mats