Hello, I have an angelfish that has(had) nice and full fins. He is about 1 to 1.5 inches long(not including fins). Tonight, I noticed that his top fin seemed partly gone, just a little, with a black tip. I don't think he had this before. Also, it seems to be coursing through the rest of his fin. I have another angelfish, 2 black moor goldfish, a fantail goldfish, and 2 guppies in the same tank. Is this fin rot or a fin nipper? Thank you in advance, I'm so worried. Also, if you know how I should fix this, please let me now ASAP.