Oh, I understand now! That is what I would do too -- just start over with fresh, new water. I didn't realize that you were talking about the transfer to the tank that the betta died in. I did the same thing when my betta died of dropsy -- I just took the tank down, and washed with the Aquarium Pharmaceutical brand cleaner. I threw the gravel away too. I thought it would be better to start with new gravel, plus I wanted to change the color. I had Bio-Spira at the time. I'm glad you're giving the other betta a home in the bigger tank!