How to re-introduce male betta into main tank after it got sick(in the main tank)?

[Alex Kwan]

Well my 10 gallon tank was going smoothly it has a sponge filter and a 50W Elite Heater(Not the Mini one). Recently I placed a magnetic algae cleaner, and a clean floating log for my lone male betta. However excited to try out the algae cleaner, I forgot to rinse it.

Anyways,I think my betta had Velvet. This is because his fins had rotted in less than a day, and his body was moving with the current(thought he was dead). So I quickly snatched him up, and placed him into a half gallon "Betta Kit" Container. I only did this since my only medicine, Bettafix only treats small containers. He has a light that's always on and keeps him warm.

So next day did a water change, and for 3 days now have added bettafix. It seems to have worked as he is much more active, and his fins are growing back well. Except one of his gills doesn't close quite properly.

Anyways if my betta does make a full recovery, how should I re-introduce him into the 10 gallon tank. Do I really have to nuke the entire tank and rinse out all the decorations,gravel, and the tank itself?? Then re-cycle it again?

Already had to do that last time he got sick.

ALSO!!! Would aquarium salt speed up the recovery. And should I add it every time I do my weekly 30% water change, so it makes my betta less prone to illness??