I would really secure them somehow, until you know for certain that they have actually attached. Do you have a spot in the tank that has a very low flow area....this is where I would put them for a few days. Don't necessarily worry about the lighting right now, they are really at this point getting use to your parameters, etc. You can always move them later. Your main interest is to make sure they don't float away, or attach to a rock in the back of the tank.