HELP! Betta skin rot

[starzfish]

Have you got a complete water test kit? Can you post water perimeters for your tap water: gh, kh, ph, ammonia, nitrite, nitrate
If so then there are others here can can better advise you on how to take care of your betta. Hopefully your tap water is compatible with a betta.

If your going to keep him, then he needs clean water and an environment where he feels comfortable. This relieves stress. You need to go ahead and re-home him into his new home. Provide places for him to hide and rest. Fake silk plants work well, with large leaves just under the water surface. There he can rest on the leaves and breath air from the surface without having to swim up for a breath.

Maybe a large ornament that he can swim in and explore. Just make sure that anything you put in his tank doesn't have sharp edges that can cut and rip his long fins.

Clean water is a must to help him heal. In a small tank like a 5 gallon you will have to change at least 60% everyday for awhile. If he doesn't get better then you will have to think of other options. Do not use any of the water from the container, pour it out.

I'm keeping him in a 15 gallon storage container for quarantine right now.

 

[Colin_T]

Do a big (75%) water change every day using water that is free of chlorine/ chloramine.

Feed the fish a couple of times a day with a variety of frozen, live and dry foods to try and build its health back up.

You can add rock salt (sodium chloride) at a dose rate of 1-2 heaped tablespoons per 20 litres (5 gallons) of tank water. Keep the salt in there for 2-4 weeks.
When you do water changes, add salt to the new water before adding that water to the tank. This will keep the salinity (salt level) in the aquarium/ plastic container stable.