I am looking for help diagnosing my male Betta. He is in an established 10 gallon filtered tank. All water parameters are good. He is not swimming around at all unless I am standing in front of him and even then he gets tired and lays on the plant. He doesn't have any white spots or anything I can see but he is clearly sick! He is still wanting to eat, I have no idea what to do to help him and any suggestions would be welcome.