there has been something wrong wit my guppy for a couple of days now he has been sitting on the bottom of the tank not really doing much all day. i was just watching the tank when my red tailed shark started trying to eat the guppy and my dannio was trying to eat it to, and then to top it all off a fellow guppy tried to eat it as well they have eaten most of its tail. why are they doing this also my other guppys are sitting around on the bottom of the tank still eating and swimming occasionally any idea what could be wrong wit them?