This worked on my betta Nolet. Hope this works for you.
1.Extra tank (About 1 gallon).
3.clean new water.
5.Betta with dropsy.
First, fill your tank up with new water. Next get 1 1/2 table spoons of epsom salt and let it dissolve.Next put your betta in the tank let him/her sit there for 1 day.
Next day clean your tank and get rid of all the epsom salt. Fill it up with new water and let your betta recover.