Regrettably, if your bathroom is too dark, your air plant will struggle. Even the mesic Tillandsia enjoy as much bright, diffuse sunlight as possible. Too little and they will struggle to survive. A bathroom with a skylight is ideal, or one with a good southern or south eastern aspect. But don’t despair! If you want a jungle garden in your closed in bathroom, consider a grow light. These are broad spectrum lights that simulate natural sunlight. A simple grow light bulb is a great option for a small half-bath, and for a more palatial northern facing room you’d do well for a stand alone unit. Air plants typically last for 2 years so setting the right growing conditions will make the most out of the time your have before they flower.