Aimlessly Disappeared

Hmm, for a long time now one of my fish (the Sunburst Wag Platy) has been acting a little lot sickly. Sometimes laying on his side in the gravel, sometimes floating aimlessly, always lethargic and slow.

The other day when I got up I noticed that I couldn't see the fish any more. Totally disappeared. I guess my crayfish had a good snack that night. :(