Tillandsias kept in the house need to be watched closely until they establish themselves in your indoor environment. They love fresh air, good light, and good humidity, and these are often not too plentiful in many homes. But, because they possess the ability to adapt to a wide range of climactic conditions, they will often grow very well indoors if you do your part to give them as much of their natural surroundings as possible.
Tillandsias kept in the house should receive plenty of strong, indirect light from a nearby window (preferably facing south). If this isn't practical, broad spectrum fluorescent lights are now available that have a light balance that is 92% actual sunlight. While this breakthrough does a lot to solve the problem of lighting, it doesn't help without fresh air circulation. Open windows or doors as much as possible but make sure the air circulates. Tillandsias don't like drafts any more than people. If you can't do that, some other form of air circulation, such as a fan, should be provided.
Watering is more criticial indoors, since there is usually a more pronounced lack of humidity, especially in homes or offices with air conditioning and/or central heating. A successful method of watering tillandsias indoors is to totally submerge them in your sink or bathtub in room temperature water containing a small amount of fertilizer (see next page). Let them sit for 20 to 30 minutes and then drain the water and let the plants drip dry. Put them back in their usual location. This should be done once a week in humid areas of the country; maybe twice a week in dry areas. Misting also helps in dry conditions, but the xerophytic plants should be allowed to dry out between each watering. Green leafy tillandsias that have cups should always have water in them. Ideally the pH factor of your water should be 6.0 or less. You can buy a pH test kit at your local tropical fish store. If your water is alkaline, add two tablespoons of vinegar per gallon of water to acidify it.
In a light airy house, most tillandsias will adapt. In a stuffy, closed-in environment they may not. Success varies from person to person, household to household, species to species, even plant to plant. Keep the plant indoors if you like If the plant thrives, terrific. If it starts looking poorly, move it outdoors.
Tillandsias grow better with bimonthly fertilization in spring and summer months. This is especially important indoors. Nitrogen is necessary for good plant growth and phosphorus and potash are necessary for good flowering and seed setting. Fertilizing is accomplished by misting them with a quarter dose of the recommended amount of a 30:10:10 fertilizer in the Spring and a 10:20:10 in the Fall. Be very careful not to overfertilize your plants. The tillandsias leaves, besides breathing for the plant, also have the added function of taking in nourishment. This makes them very sensitive to chemical burning from overfertilizing. It is much safer to underfeed than overfeed.
If all of this sounds too complicated, don't worry about it. Do what you can and the plants will probably grow like weeds. Remember above all that tillandsias are among the most carefree and hardiest of all houseplants.