my clown loach is going black Help

[red-devil0602]

My 6inch clown loach is acting really weird swimming up and down the height of the tank like mad. Also he looks like he can't shut his mouth and the orange part of his body is staining black

 

[WILDER]

Please post water stats in ammonia,nitrite,nitrate,and ph, what size tank, how many fish and which type.