Hey, he is doing well. I thought he was kinda sad but he flared at my twice (yesterday and today) which he never does so maybe he is fine solo. I cleaned the other side really good and removed any decor and one plant that was on its way out anyways. I changed the water and am changing again tomorrow. I figured I would water a week or two to see how he is and by then the tank water will have been refreshed a couple times and vacuumed a few. Then if all seems fine, I may consider stocking the other side or just giving him run of the 20g( assuming I can get the divider out without having to move the tank- i put it on a shelf and it is impossible to open the lid all the way where it is, only 50%). I didn’t want to make any more changes until I am certain sickness is gone and not stress him out unnecessarilyBy the way, how is your other betta in that divided tank doing? I don't think we ever came up with a definitive answer regarding whether to clean the entire tank and its contents, or all the decorations and a 50% water change, or...?