I have a beautiful Male dwarf guorami, he has been super healthy up to this point. Today I realized he was sitting at the bottom of the tank, (which is where he prefers to sleep most of the time), but I noticed he would start sinking after he made his way to the top for air. He looks more pale, and did not eat today. I change his tank regularly and just did a 50% change. Ammonia levels are fine, as I've never had an issue with them and there are no signs of ich. Hes partnered with a small female guppy (they always get along, despite small annoyances, but they never nip at each other). What can I do? Any advice on what might be causing this sort of behavior? I'm really worried.