I have a beautiful young blue acara that hasn't eaten ANY food in well over a month. I got it from a LFS about 6 months ago. It was about 1 inch long, and grew maybe 1/2 inch since. Initially, for a few months, he (or she?) had a good appetite, then he just stopped eating. There was no provocation, no new fish, and NO visible sign of disease, other than a concave/sunken lower abdomen due to starvation, and less blue luster. I've treated with a broad range of antibiotics including prazipro - praziquantel (tape, flat, flukes), expel - levamisole (nematodes, round, hook), paracleanse - praziquantel and metronidazole (flukes, velvet, lice), lifeguard all-in-one - imidazolidinone, Pimafix and Melafix. All treatments were completed, some repeated, and water changes were as directed. The poor thing has had Zero response to treatment. I've tried numerous foods including frozen carnivore blend, beef heart, mysis/brine shrimp, sinking algae wafers, sinking carnivore wafers, bloodworms, and flakes. Food has literally hit him in the face with no response; no interest. Water quality is kept pristine in a 15 gal Fluval quarantine tank with filter, bubbler, no carbon, and heater set to 82. He's been in isolation for over a month with no progress. He remains interactive, will come up to the glass, etc, but Zero apatite. There are no spots, slime, or other external signs of disease. I've seen no evidence of worms (though treated aggressively 'in case'). No other fish in his former community tank got sick. They are all flourishing. The only clue he gives me is that intermittently he will take a big 'gulp' with his mouth (second pic). He has no labored breathing at all, but he does this 'gulp' fairly frequently and sometimes in clusters. He never did this before getting sick. I haven't been able to see any mass or obstruction in his mouth. Any thoughts/advice/remaining treatments to try are greatly appreciated! He's a great fish, and it hurts my heart to watch him die slowly like this.