Torn Tail Fins
 

all of my fish have there tails torn up there was 2 mosquito fish in there and that was when there tails looked all torn up but by male guppies tail fin is looking like it is deteriorating. Could it be fin rot

Whats the tank size they are in? Can you post your water parameters and tank mates please. We need a little more information before we can help you, and a picture would be awesome too!

Hows long ago did you get these fish? Did you cycle the tank?

Chinese algae eater could also be the problem.they don't play nice with others sometimes. They are not from china, they only do a fair job of eating algae when they are young and as they mature they can become aggressive towards other fish. It could be wreaking havoc after lights out of an evening.