Thanks for the info! Lets start with this- what exactly is wrong/different with him besides the minor fin rot on his tail? In the video, his gills look extremely red/inflamed- is this the case? Are there wen issues as well? I would start by doing atleast a 50%
wc with temperature matched properly conditioned water. You have what looks like in the pic detectable ammonia & nitrite. Start by addressing any water quality issues first- meds do not help if theres issues with the water. I would then add some aq salt & start feeding him a full course of treatment of the medi-gold. Premix 2 flat tablespoons of aq salt in a cup of tank water & add slowly over 48hrs. When you do a water change, add back only the salt you remove (ie, 50%
wc, add back 1/2 original dose or 1 flat tablesp). Make sure you test your water daily & do a water change if theres any detectable ammonia and/or nitrite- if theres none, I would do a water change every other day to provide the healthiest water you can for him so he can heal up quickly. Please ask if you have any questions!