That woudl be fine in a 10 gallon. I had that setup for awhile with no problems. White Clouds do best at lower temps as other say, but it is generally the higher oxygen levels in the lower water that is needed. So keep the aeration in the tank high and keep some plants and you will do fine.
My one problem was that my betta wasa very slow and picky eater, he always liked to stare at the food for awhile. The White Clouds though wanted to grab as much as they could really fast. I essentially trained them to eat from separate corners of the tank. Might not be the same with you, just keep your eyes open to it.
It was always funny to watch teh gang of White Clouds start to sneak up on the betta, he would turn and flare and chase them away. All good fun and no nipping at all.