I have a blackmoor goldfish who lives in a 20 gallon tank. He appears happy and healthy and all of the water parameters are exactly where I want them, however, I find that he often darts to the top of the tank and breaks the surface of the water, and it looks like he is trying to jump out of the water. Should I be concerned or is this normal goldfish behavior? Thanks! I have also attached a picture of him in his tank as well.