Fish Death - please help?

good idea not replacing him...he was beat up and probably had brain damage...the respitory system had collapsed cus of the fight most prbly frm ramming into the fish...this and constant strees could have caused brain damage which also explains the poop....i had this happen recently between a tin foil and a leperonius:( that was one sad week,,,,make sure the others didnt sense the ammonia sent out by the stressed fish :Dhappy fish keeping