Houseplants tip: Save the water from cooking pasta. Let it cool, then use it to water houseplants.If the soil of your houseplants get algae, loosen the dirt in your pots periodically. Open the doors and windows when temperatures permit to give your house a change of air. This will benefit you and your houseplants. Re-invigorate your houseplants by removing the top 1/4 inch of soil and top-dressing with fresh potting soil.