I have had a Male Kribensis in my 125 Gallon Community since I first got the aquarium 2 years ago. I unfortunately lost the female that he had paired up with a little more than a year ago when the tank had a very bad and aggressive Ich breakout. My male Krib survived the issue, and has been a picture of health ever since. He is fully grown now at about 4 inches. He is an absolutely beautiful specimen, but recently has been breathing very heavy, hiding a lot, and not eating. He first started breathing heavy a few weeks back. After the first week of heavy breathing with no appetite, he seemed to recover and got his appetite back for about a week or so but is now back in the same shape again, maybe even a little worse with a more rapid breathing rate than before. All other fish in the tank seem fine, acting like their normal rambunctious selves. All water parameters are normal: Ammonia-0, Nitrite-0, Nitrate-15, Ph-7.
I can run through a detailed stocking list if anyone would like for me to, but right now I will only mention that the newest addition to the tank (added about a month ago) is a native Orangespotted Sunfish that is about 2 inches in size. I have not witnessed any fighting between these two, as the Sunfish seems to get along perfectly with everyone in the tank and is always begging for food alongside my full grown angelfish. I did notice about a week ago that the sunfish had a small chunk taken out of his tail fin. It has since grown back and is almost fully healed at this point. The Krib has no signs of nipped fins or other damage. I know that one scenario could be that these two are fighting when I'm not looking. If that were the case, then it would seem that the sunfish would be completely stressed as well, which is not the case. The nipped tail fin didn't even phase him... Everyone else in the tank have been together for well over a year, so I can't imagine that aggression between any of them and the Krib has just recently started (but I know this is also still a small possibility). The Krib and Angelfish have always been good pals. Other candidates for aggressiveness are a Spotted Pictus Catfish (has been in the tank with the Krib for 2 years), and an also recently added 2 inch Red Tail Sternella Pleco that mostly just hides.
Another scenario could be the recent addition of java moss to the tank. When I first put it in the tank, I observed my Krib try to eat it. It actually seemed to get caught in his throat and he had a little trouble spitting it back out. I can't seem to get all of the java moss back out of the tank at this point, and I'm worried that he may be eating on it periodically, causing the heavy breathing because he is unable to digest it properly. Could it still be caught in his throat?
Another thought that I had is his age. He wasn't fully grown but fairly large at about 2 inches when I got him. I read that they have a lifespan of 5 years, and I know that can be reduced by stress (and the tank did experience the bad Ich breakout over a year ago). I have no idea how old he was when I got him, but I can't imagine he was more than a year old because of his size.
We absolutely love our Krib. My wife named him Kale early on, and he is one of our favorite fish, so it has been very tough to watch him struggle like this. Any help or advice is greatly appreciated.