I bought 3 guppies just over a week ago for my 75l tank with 6 Neon Tetras and a Bronze Cory. They were all eating fine and nothing was unusual until I did a head count and was missing one Guppy to be found looking very normal, nothing different except it was in the filter and dead. I can do a water check tomorrow because I have school but does anyone know why this may be? The tank was cycled and planted before they were introduced.