Oscars can be a little bit subdued and often appear miserable and sulky, just sitting on the bottom of the tank doing nothing. However, they shouldn't do this for long and from my experience, a healthy fish will often react when you approach the tank, ie coming to the front of the tank in anticipation of food. If there fish just sits around and doesn't move for long periods of time then this can be a cause for concern as it will be just like us wanting to stay in bed, or just lie on the sofa not moving because we don't feel very well. Always check your water conditions if you suspect something might not be right
