Over night I noticed a neon Tetra has a black eye or growth. Any ideas what it is? Also. With only 5 neon tetras (now 4) and 1 Pleco. Mysteriously a Tetra dissapered one day (no, there's no other way how on earth he could have dissapered) it's unexplainable. Just wondering what on earth would have caused the black eye and maybe any ideas why a Tetra would disappear?