I don't know what it is. One of my poker buddies ejected that bad boy from his 75 because it killed everything. It has done the same thing with me. Only fish left are the big Goldsaum and a common pleco. I've had that fish about 4 years now. Plants and drip system only on this 58 Gal tank. Thanx for all the kind words. I think the reason the top fin is so long is there aren't any fish in the tank with him to nip it off. Looking for a female now.