I added a female guppy and some glolight tetras from petco to my 30g, without quarantine first, and within days most of my fish were dead or dying. I have the surviving guppies and the tetras quarantined and the guppies especially are in really bad shape.
I identified ich pretty quickly and have been succesfully medicating for that - but there's something else going on - all the color has drained out of the guppies bodies/tails - they are becoming a pale gray, like ghosts. The male's tail is turning white and falling apart.
I'm amazed they are still alive. Does this sound familiar to anyone? I don't have a camera so I can't post a pic...