Turn Fish Tank Into Terrarium – The Ultimate Guide To Repurposing
Do you have an old aquarium sitting in your garage, gathering dust and taking up valuable space? You aren’t alone; almost every seasoned aquarist has a “spare” tank that either has a small leak or simply isn’t being used for fish anymore.
If you are looking for a way to breathe new life into that glass box, you are in the right place. Learning how to turn fish tank into terrarium setups is one of the most rewarding ways to stay in the hobby while exploring the world of terrestrial and emerald-green tropical plants.
In this guide, I will walk you through the entire process, from preparing the glass to choosing the perfect substrate layers. By the end of this article, you’ll have the confidence to create a thriving, self-sustaining miniature ecosystem right in your living room.
Why You Should Repurpose Your Old Aquarium
There is something incredibly satisfying about recycling. As fish keepers, we often invest heavily in high-quality glass tanks, and it feels like a waste to let them sit empty.
An aquarium is actually the perfect vessel for a terrarium because it is designed to hold weight and provide clear, 360-degree views of your hardwork. Unlike traditional pots, the high walls of a tank allow you to control humidity levels and create deep substrate beds.
Whether your tank has a small chip that makes it unsafe for water or you just want a lower-maintenance hobby than a high-tech reef tank, a terrarium is the logical next step. It’s a bridge between the world of aquascaping and traditional gardening.
Step 1: Preparing Your Tank for Its New Life
Before you start adding soil, you need to ensure the tank is structurally sound and clean. Even if it won’t hold 20 gallons of water, it still needs to be sanitized to prevent mold or algae from taking over your new plants.
Cleaning the Glass
Use a mixture of distilled water and white vinegar to scrub away old hard water stains and calcium deposits. Avoid using harsh chemical cleaners or soaps, as these residues can linger in the silicone and harm sensitive mosses or ferns.
Checking the Seals
While the tank doesn’t need to be 100% watertight for a terrarium, the silicone seals should still be intact to prevent soil and moisture from seeping out. If the silicone is peeling, you can easily scrape it away and apply a small bead of aquarium-safe silicone to keep the structure rigid.
Step 2: Choosing Your Terrarium Style
The beauty of a glass tank is its versatility. Before you buy your plants, you must decide what kind of environment you want to replicate. This decision dictates everything from your choice of substrate to your lighting setup.
The Tropical “Closed” Terrarium
This is the most popular choice for converted fish tanks. By using a glass lid, you trap moisture inside, creating a high-humidity environment. This is perfect for tropical species like Fittonia, ferns, and various types of moss.
The Arid “Open” Terrarium
If you prefer succulents and cacti, you’ll want an open-top setup. These require maximum airflow and very little humidity. An old aquarium works well for this, but you must ensure your drainage layer is extra deep to prevent root rot.
Step 3: The Secret to Success – The Drainage Layer
In a traditional garden, excess water drains into the earth. In a glass tank, there are no drainage holes. This is where most beginners fail when they turn fish tank into terrarium habitats.
Using LECA or Gravel
You must create a “False Bottom” using Lightweight Expanded Clay Aggregate (LECA) or coarse aquarium gravel. This layer, usually 1-2 inches deep, acts as a reservoir for excess water, keeping it away from the roots of your plants.
The Importance of a Barrier
To prevent your soil from sifting down into the drainage layer and turning into a muddy mess, you need a substrate barrier. You can use a fine plastic mesh, window screening, or even a layer of dried Sphagnum moss.
Step 4: Crafting the Perfect Substrate Mix
Standard potting soil from a big-box store usually isn’t enough for a long-term terrarium. It tends to compact over time, suffocating the roots. To act like a pro, you should create a well-draining mix.
The “ABG” Mix (Atlanta Botanical Garden)
This is the gold standard for terrarium enthusiasts. It typically consists of tree fern fiber, milled peat moss, charcoal, and orchid bark. This mix provides excellent aeration and holds moisture without becoming waterlogged.
Adding Horticultural Charcoal
A handful of activated charcoal or horticultural charcoal is essential. It acts as a natural filter, absorbing odors and preventing the growth of “sour” bacteria in the closed environment.
The Best Plants to turn fish tank into terrarium Success
Not every plant is suited for life behind glass. You want species that stay relatively small and can handle the specific microclimate of your tank.
Top Picks for High Humidity (Tropical)
- Fittonia (Nerve Plant): Known for their striking leaf veins, they thrive in damp conditions.
- Creeping Fig (Ficus pumila): An excellent climber that will eventually cover your background or hardscape.
- Lemon Button Fern: A hardy fern that stays small and adds a delicate texture to the midground.
- Java Moss: Yes, the same moss you use in your shrimp tanks! It grows beautifully on land if kept moist.
Top Picks for Low Humidity (Arid)
- Haworthia: These succulents have a structured look and handle the indirect light of a terrarium well.
- Echeveria: Beautiful rosette shapes that add a pop of color.
- Jade Plant (Crassula ovata): A slow-growing succulent that looks like a miniature tree.
Step 5: Hardscaping and Design Principles
Just like aquascaping, a terrarium needs a focal point. Use natural elements to create depth and interest. This is where your inner artist comes out!
Using Driftwood and Rocks
Pieces of Spider Wood or Manzanita look fantastic in a terrarium. They provide height and a place for climbing plants to attach. For rocks, consider Dragon Stone or Seiryu Stone, which add an aged, mountainous feel to the landscape.
Creating a Sense of Scale
Place larger plants and rocks in the back and smaller ones in the front. By sloping the substrate from the back down to the front glass, you create a 3D effect that makes the tank look much deeper than it actually is.
Lighting and Environmental Control
Your plants need light to photosynthesize, but the glass of an aquarium can act like a magnifying glass. If you place your terrarium in direct sunlight, you will likely cook your plants within hours.
Artificial Lighting Solutions
For most setups, a standard full-spectrum LED aquarium light is perfect. If your light has a timer, set it for 8-10 hours a day. This provides consistent energy without the risk of overheating the enclosure.
Ventilation and Airflow
If you notice excessive fogging on the glass, your terrarium may be too wet. Simply crack the lid for a few hours a day to allow fresh air exchange. This prevents mold and ensures your plants can “breathe.”
Maintenance: Keeping Your Ecosystem Healthy
One of the best things about a terrarium is that it requires much less maintenance than a fish tank. There are no water changes or filter cleanings! However, it isn’t entirely “set it and forget it.”
Watering Techniques
In a closed terrarium, you might only need to add water once every few months. Use a spray bottle with distilled or RO (Reverse Osmosis) water. Tap water can leave unsightly mineral streaks on the glass and may harm sensitive mosses.
Pruning and Grooming
Tropical plants can grow surprisingly fast in a high-humidity environment. Don’t be afraid to trim back overgrown leaves with a pair of sharp aquascaping scissors. This encourages bushier growth and prevents one plant from shadowing others.
Common Challenges When You turn fish tank into terrarium
Even with the best planning, you might run into a few hiccups. Don’t worry—most of these are easy to fix if you catch them early.
Dealing with Mold
White, fuzzy mold is common in new setups as the ecosystem balances out. Usually, increasing airflow or adding a “clean-up crew” of Isopods and Springtails will solve the problem naturally. These tiny bugs eat decaying matter and mold, keeping your tank pristine.
Algae Growth on Glass
If you see green algae growing on the glass near the substrate line, it’s usually a sign of too much light. Move the tank further from windows or reduce the “on” time of your LED lights.
Frequently Asked Questions (FAQ)
Can I turn a leaking fish tank into a terrarium?
Absolutely! Since a terrarium only holds a small amount of water in the drainage layer (not the full volume of the tank), a small leak near the top or a minor structural crack is usually fine. Just ensure the bottom 2-3 inches are sealed well enough to hold the moisture in the drainage reservoir.
Do I need a lid for my terrarium?
It depends on the plants. For tropical plants that love humidity, a glass or acrylic lid is essential to maintain the moisture cycle. For succulents and cacti, you should leave the top open to ensure dry air and prevent rot.
Is it cheaper to keep a terrarium than a fish tank?
Generally, yes. You save money on expensive filters, heaters, water conditioners, and fish food. The primary costs are the initial substrate, plants, and lighting. Once established, the ongoing costs are almost zero.
Can I put animals in my converted terrarium?
Yes, but with caution. Small invertebrates like Isopods, millipedes, or snails thrive in these environments. If you want to keep reptiles or amphibians, you must ensure the tank provides proper ventilation and heat gradients, which may require modifying the tank further.
How long will a terrarium last?
With proper care, a terrarium can last for years. Some famous “sealed” terrariums have survived for decades! As long as the plants have light and a small amount of recycled moisture, the cycle will continue indefinitely.
Conclusion: Your New Green Sanctuary Awaits
Learning to turn fish tank into terrarium displays is a fantastic way to extend your love for nature. It allows you to experiment with different textures, colors, and biological processes without the constant worry of monitoring ammonia or nitrate levels.
Whether you choose to build a lush, misty jungle or a stark, beautiful desert, your old aquarium is the perfect canvas. It’s a rewarding project that brings a piece of the outdoors into your home, providing a sense of calm and accomplishment every time you look at it.
So, go grab that old tank from the garage, clean off the cobwebs, and start building. Your plants are waiting! Happy planting from all of us here at Aquifarm!
