i looked at my take today and there is something up with my male guppy. nothing looked wrong last night. his back tail is gone, well most of it. he also looked like he changed color. i tested the ammonia it was 0 and the nirites are also 0. the tank is 20 gal with only 4 guppies and some ghost shrimp. the tank has been running a little hot so i have been puting in frozen bottles of water. i will try to get pics some time tonight. does anyone think they know whats up?