no tail chiclid

Question
I am new to the chiclid world.  I just started living with a man who has a tank full of them.  He bought me a baby and he did well for a couple of days, racing about and seeming to have a good time.  Soon he began hiding in the rocks all day only coming out to eat a piece or two.  He was not swimming well, seemed out of balance and disoriented.  We checked the levels in the water and everything seems fine.  I came home the day before yesterday and he was vertical in the rocks, tail down, at the bottom of the tank.  Yesterday we could not locate him at all, even when we moved the rocks!  He finally came out, still wobbly and disoriented from down below in the gravel and we noticed his entire tail is missing.  Was he attacked?  Is it the water?  Do we need to help him on his journey to chiclid heaven, or might he survive somehow?

Answer
I do not know if there is another fish in with him but he may have been attacked by his tank mates if they are in there. If he does not have tank mates it may be that he does not feel safe and you should add more plants and a background, another thing is the gravel is probably what did the damage or the rocks, if you think he will not live much longer and you want to help him along (I'm talking about death just to be clear) you can humanely kill him by putting him in a cup of water and placing it in your freezer or you can sever the spine with one quick motion.