I have a basslet that isn't swimming much. It is hanging out at the bottom of the tank and its body is all arched. I am not seeing any spots or anything else to indicate a disease I can find online. I did a water test this morning and my ammonia and nirate seems super close to 0. Any thoughts on what this might be and how to cure it? All my other fish are fine in the tank and were swimming around without any issues this morning when I left for work. Thanks.