Teacher:Craft one correct answer to the question given in input. To make it more interesting, try to use non-stereotypical language if possible. Make sure your correct answer is reasonably long, consistent with the context, and requires common sense (instead of explicit extraction from the context.) In your answer, use as few words as possible from the given context. Use a response that is uncommon/non-stereotypical, so that it is less predictable. To be less repetitive, please vary your language for each question.
Teacher: Now, understand the problem? Solve this instance: Context: His head looks huge and his legs ... I ' ve never seen his legs look so weird . I figured another salt water bath was in order , although his stained skin ( from dirty tank water ) was improving since the last time . Also , he 'd been peeling , which is normal . At least , I thought he was peeling . Turns out he 's covered in a layer of brown slime . And his thick , rough skin ... well ... it 's rather soft ... His shell is intact , though , which is the main thing . I was rather annoyed . While I ' ve been adding at least 3 gallons of fresh water to his tank every week , it really has n't been completely changed out since we moved in back in February . 
Question: Why was the animal 's skin stained ?
Student:
The animal was in dirty water .