all the guppies are now dead one by one , they were put in an established tank, no illness in the tank that i know of .seemed happy for the first eight days ,then one goes missing ,found him the next day,when another looked pale and lifeless, but still alive ,next morning he was gone to..this went on,nearly every day or two days losing another,one even went belly up in front of our eyes,hejust turned over and dropped to the bottom,7 lost guppies in all .the water checked out ok, and if it was shock wouldnt they have all died at once,added melafix after first one .any ideas on this one ,as ive never had this situation before and dont want it to happen again . hoping someone can help best wishes to all who put so much into this site.. jackie