If you don’t want to restock your fish tank because the kids lost interest or your life is just too busy to maintain an aquarium, why not repurpose the tank into something useful?
Upcycling is an incredibly popular hobby and can be a great way of giving an old, redundant object a new lease of life without consigning it to a landfill. According to the U.S. Environmental Protection Agency, in 2018 alone, we sent about 7.6 million tons of glass to U.S. landfills. Glass takes an estimated 1 million years to fully degrade, so any glass you throw in the trash is going to be sitting in that landfill for a long, long time.
With that in mind, here are three fun ideas to help you repurpose your old fish tank into something you can use right now.
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1. Coffee Table or Side Table
Fish tanks are built to hold the considerable weight of gravel, water, fish, plants, and items of décor. So, a large redundant fish tank is ideal for safe conversion into a coffee table or side table. Here’s how to repurpose your fish tank into a small table.
Start by cleaning out the aquarium completely. Use a scraper to remove any stubborn algae and give the glass a really good polish using glass cleaner and a soft non-abrasive cloth.
The glass tank will be the base of the table. While you could leave it empty, it will make a much more attractive piece if you fill it with something decorative or colorful. So decide what look you want for the table and fill the tank with whatever you want. For example, responsibly sourced multi-colored sands, pebbles, driftwood, and shells can look very effective.
Now, you need to choose a top for the table. That could be clear glass, repurposed wood, or even a mosaic that you design and make yourself.
Place the top on the glass aquarium base, and the job is complete.
2. Herb Garden
You can also repurpose a fish tank into an herb garden. It’s important to allow at least 3 to 4 inches between each plant, so the larger the tank you have, the more herbs you can grow.
Wash out the tank, using a few drops of bleach to disinfect it. Rinse the tank thoroughly and allow it to air dry.
Cover the bottom of the tank with an inch of pebbles or gravel so that the water doesn’t pool around the plant roots.
Add a thin layer of activated charcoal on top of the gravel to keep humidity levels down.
Although it’s not essential, I recommend adding a layer of sphagnum moss to stop your potting mix from working its way down into the gravel and affecting the tank’s drainage.
Add a lightweight potting soil to a depth of at least 6 inches. Then moisten the soil evenly but not so that it becomes waterlogged. If the soil is too wet or heavy, the plant roots can’t breathe.
Now, you can plant your herbs. Arrange the planting so that you have the tallest herbs at the back of the tank and the smaller ones toward the front. Alternatively, if you want to view the herb garden from both sides, plant the taller herbs in the center of the tank with the smaller ones around the outside.
You can add pebbles, driftwood, or other decorations to the herb garden if you want to.
Most herbs require at least six hours of sunlight per day to grow, so put your herb garden in a location where it gets plenty of bright sunshine. If you need to boost light levels, add low-energy, LED grow lights to the setup.
Water your herb garden so that the soil is damp. To avoid overwatering, I use a plant mister to moisten the soil without getting the foliage wet.
You might not need to water your herbs every day. Use your finger or a wooden spoon handle to check if the soil is moist down to the plant’s roots. If so, you don’t need to add more water.
During the spring and summer growing season, feed your herbs with a weak solution of water-soluble fertilizer, as per the manufacturer’s recommendations.
3. Aquaponics for Growing Food
An aquaponics system enables you to grow food and continue keeping fish, so it’s a win-win. Once the aquaponics system is up and running, it takes less maintenance than a regular fish tank. The fish waste provides nutrients for the plants, and the plants keep the water clean for the fish, so the setup is almost self-sustaining.
Follow these steps to repurpose a fish tank into an aquaponics system.
Set up the fish tank as you would normally but without a filtration system — the plants will do that for you. Include a pump to circulate the water through the grow bed to feed the plants and then back into the tank.
Fill the tank with dechlorinated water and allow the aquarium to cycle for four to six weeks before adding your fish.
The tank must be fully cycled so that colonies of beneficial bacteria can be established. These bacteria process fish waste into nitrates that the plants then use as food.
Now, build your media bed in which the plants will grow, as shown in this YouTube video.
Fill the media bed with clay pebbles, which are excellent for moisture retention and won’t alter the water pH.
Once the tank is fully cycled, you can add your fish.
There are lots of different species to choose from, depending on the size of your tank. Goldfish produce lots of waste and are ideal for aquaponics if you have a tank of over 20 gallons. However, small, ornamental species, such as guppies, mollies, tetras, and the like, are ideal for smaller setups.
The best choice of plants for small aquaponics setups are leafy greens, especially lettuce, watercress, basil, and kale.
Gently place the plant roots into the clay pebbles, ensuring that the roots can reach the water so that the plants can obtain all the nutrients they need.
Once the system is up and running, maintenance is pretty straightforward.
Your fish need a high-quality diet of pellet or flake food, supplemented with frozen meaty foods for variety. I recommend that you do not use live foods in an aquaponics system as that could import parasites and diseases into the tank. Feed the fish two to three times each day, only offering what they will consume in a couple of minutes.
Test the aquarium water every week. Ammonia and nitrite levels should always be zero, and nitrates should be negligible if the plants are doing their job right!
Prune and tidy the plants as you would normally do, removing dead leaves and damaged stems.
So Many Upcycling Opportunities
Whether you want to create an herb garden, build a unique coffee table or side table, or grow your own veggies, repurposing an old fish tank can be a fun upcycling project. I hope the ideas included in this guide have whetted your creative juices! What other uses can you come up with for your old fish tank?
About the Author
David Girard is managing editor at Tankarium.com. Fishkeeping expert David is a lifelong hobbyist and an expert in keeping and breeding betta fish.
This article was originally published on July 23, 2021.