My five year old Oscar is grumpy. Well actually he's been quite inactive for the past few days. Basically sits on the gravel an does nothing. The up keep is tip top. Weekly water changes and checks. Right now the Kh is a little low, but nothing to worry over. His appetite has greatly diminished. He lives in a 125 gal tank with about a dozen little tiger barbs and 3 to 6 danio's who's numbers fall often sinec they're just a little snack.. The water is cleam, balanced yet he does nothing... I've raised him for 5 years dont know what to do???? Any help would be greatly appreciated.