Indoor gardening can present a challenge. Are your plants getting enough heat? Moisture? Light? Is the humidity high enough for them? Creating a small, indoor greenhouse out of an old aquarium can present the answer to all of these questions. With an indoor greenhouse to start seedlings, your plants will be ready to go before spring even starts. As a bonus, indoor greenhouse gardening with an aquarium can make the care and keeping of tropical flowers and plants a breeze.
Procure an aquarium suitable for your needs. The best types of aquariums are the ones termed "community tanks," which are wide and deep. Tanks labeled for show are often shallow and tall, and do not lend themselves to greenhouse gardening. Tanks that contain 30 gallons or more are recommended, as they can hold more plant life.
Place a layer of activated charcoal at the bottom of the aquarium. This keeps the air fresh and can be found at any fish or pet supply store.
Line the bottom of your tank with gravel. If you decide to leave your plants in containers within your fish tank greenhouse, the gravel will filter off any unused water. Similarly, a layer of gravel will create a filtration system if you decide to add potting soil and plant the greenery directly into the aquarium.
Decide whether you will pot your plants before placing them in the greenhouse. Leaving them in the pots means that you can remove them for easy cleaning and examination and makes for easy removal if any problems arise. Planting them directly in the soil means less hassle, but less flexibility.
Add a layer of potting soil if you are planting the seedlings directly in the greenhouse. Choose plants that will not exceed the size of your tank if you decide to pursue this method.
Place your plants in the greenhouse. Make sure they are positioned an optimal distance from each other. The label for the plants or seedlings will say how much spacing is needed for each.