Alright, IDK what this stuff is. I've decided I got this "stuff" with bloat 4 months back. The bloat killed some, but I've also noticed some white stuff on their mouth. I spent some serious $$$ treating the whole 50 gallon tank with maracyn plus, assuming it was cottonmouth, and nothnig improved. The fish that had it died from bloat. Now i've noticed i've got an electric yellow who's got it. GRRRRR! His mouth is almost detached, when he eats you can see it go up and down...it's pretty gross! Any idea as to what this is, I'll get some pics up tomorrow.