I've never had any issue. When I have a new male come in that needs QT'd I'll often times put him in a 1 gallon (or so) critter keeper or net and float him in the sorority so he has stable heat. They definitely try to go after the girls, but after a few days, like LBF said, they end up realizing they are stuck there and calm down.
But you always have to be careful about him being able to escape. Try to cover it with something if at all possible.