Yes, they are safe to use with betta's. Is the room your fish is housed in dark? If it's not and has some source natural light just turn the light on in the late afternoon when it's starting to get dark out, and turn it off when you go to bed. If the room if dark you can turn it on when you wake up. Of course if the room does have natural light you still can turn it on when you wake up, I have just found that it creates more algae and I have to clean the water more frequently if I do that. It's basically just up to you.