I Have a little bit different way of doing it... My guys all live in 1 gallon bowls. All are healthy, happy, and very unstressed, and I do 100% water changes every week. To be less stressful on them all, I keep an extra gallon bowl around, and I prepare it with clean water, stress coat, correct temp, and everything, and transfer the first betta directly into it. Then I clean the bowl I just removed him from really, really well, fix it up, and put the next guy into that one, and so on... The result: the fish only change locations one time to an identical bowl, rather than being switched to a holding cup or having the invasion of a partial change. They are perfectly content, and the only time I don't use this method is with new fish until I'm sure they are as healthy and happy as the others, so that I don't accidently transfer any new diseases. It seems to be less stressful on them this way than the other ways (which I've tried), and I've never had my babies get sick this way.