I bought two female guppies yesterday. Today I was gone all day; when I got home one of them was dead. My question is this: The other guppy and the cory in the tank seem to be acting perfectly fine, so I'm guessing that the problem is not water quality (haven't had a chance to test), though I did a partial water change anyway. That leaves the possibility that something was wrong with the guppy. I don't want to leave the other female alone for any longer than I absolutely have to, but I don't want to buy a new fish if my remaining girl (Dubh) may be sick or if the other guppies at the lfs may be sick. Should I go buy a new guppy tomorrow, or should I wait until I am certain that Dubh and Amaethon aren't sick? I can buy the guppy from a different store, and I was also planning on buying another cory.