I am not a beginner to keeping fish but am a beginner to trying to help a fish that isn't feeling well. I know some of the first questions are going to be about my perimeters but rest assured my tank water isn't the problem. Tank is a 55 gallon and has been cycled for well over 2 years. It gets a 30% water change every week. Nitrates may be a bit high at 40. I will do an extra water change this week to get them lower. One of my long finned black skirt tetras hasn't been feeling himself for the past few days. He is about 2 1/2 years old. He lives with 5 other LFBST's in a community tank with neon tetras, danios, cory's and a BN Pleco. He is the only one that doesn't feel well. A couple of days ago I noticed he wasn't eating. He still gets excited at feeding time but doesn't eat. He goes to the top and for an instant sticks his nose out of the water but I only see him doing it during feeding time. He appears to go toward the food but jut swims past it. I see nothing about him that would lead me to believe he has parasites or any sign of any outward problem. His fins are still long and flowing and in perfect shape and the darkest black of all of them. He does swim in jerky motions instead of his normal smooth movements though. I have been seeing Peroxide being used in some cases and was wondering if it would help in this case since there are no outward signs of disease. Since I have never had to try to help a sick fish I am lost. I won't just throw anything at him and hope it helps. I am just hoping someone has experienced this and was successful in treating it. Since there are no outward signs I can't provide any other symptoms. I don't have a LFS so will either have to use something I have on hand or it will have to be ordered online. I have peroxide and aquarium salt. I have tried to feed peas in case he has a tummy ache but since he isn't eating it hasn't helped him. I have considered dissolving an aspirin or maybe an antacid in some tank water and putting him in it for a little while. Do any of y'all think it would help or could it make him worse? Thank you all for reading this novel.