Chaeto is safer, but Caulerpa is more effective. Gracyllaria is another option which is pretty comperable to Chaeto. It's a bright red free-floating, branching algae that as a bonus is rather pleasant to look at as well.
Probably not news to you, but since you've gone with Caulerpa, be sure to trim it back at least once every two months, or it may go sexual on you and pollute your tank. You can also keep it on a 24 hour lighting schedule (one of the few macro algaes that will tolerate this), and that is also supposed to prevent a sexual event.