20 Gallon Hexagon Fish Tank – The Ultimate Guide To Setup, Stocking
Finding the perfect balance between aesthetics and functionality is the holy grail of fish keeping. You likely agree that the unique, 360-degree view of a 20 gallon hexagon fish tank is one of the most striking ways to display an aquatic ecosystem.
I promise that by the end of this guide, you will know exactly how to overcome the common challenges of vertical tanks, from oxygenation to aquascaping. We will preview the best equipment, the most compatible fish species, and the “pro-tips” I’ve gathered over years of managing these tall beauties.
Setting up a 20 gallon hexagon fish tank is an exciting journey that transforms any corner of your home into a living piece of art. Don’t worry—this setup is perfect for beginners if you follow the right steps!
Understanding the Unique Dynamics of a Hexagon Tank
A hexagon tank is fundamentally different from your standard rectangular aquarium because it prioritizes vertical height over horizontal swimming space. This “column” style creates a beautiful silhouette, but it changes how we think about biology.
The most critical factor to remember is the surface area to volume ratio. Because the top of the tank is narrower than a long tank, there is less interface for gas exchange.
This means you have to be more intentional about water movement. Without proper surface agitation, oxygen levels can drop, which is why choosing the right filter and air stone is vital for a healthy environment.
Footprint vs. Swimming Space
In the world of fish keeping, “footprint” refers to the floor space of the tank. A hexagon has a smaller footprint, which means bottom-dwelling fish have less “real estate” to claim as territory.
When planning your 20 gallon hexagon fish tank, think about fish that enjoy navigating tall structures rather than those that need to “sprint” from left to right. This isn’t a limitation; it’s simply a different way of designing.
The Visual Advantage
The greatest benefit of the hexagon shape is the multi-angle viewing. You aren’t just looking at a flat pane of glass; you are seeing the depth and movement from six different sides.
This makes it an incredible centerpiece for a room. Whether it’s placed in a corner or used as a room divider, the 20-gallon size is large enough to be impressive but small enough to fit on most sturdy stands.
Equipment Essentials: Filtering and Lighting Your Hexagon
Because a 20 gallon hexagon fish tank is deeper than a standard 20-high or 20-long, your equipment needs to be powerful enough to reach the bottom. Standard “kit” filters often fall short here.
I always recommend upgrading your filtration to ensure that water is being pulled from the lower levels of the tank. This prevents “dead zones” where waste can accumulate and rot.
Choosing the Right Filter
A Hang-On-Back (HOB) filter is a popular choice, but you must ensure the intake tube is long enough to reach at least halfway down the tank. This encourages vertical circulation.
Alternatively, an internal power filter or a small canister filter can be even better. Canister filters allow you to position the intake and output specifically to create a gentle “swirl” that keeps the water oxygenated.
Lighting for Deep Water
Lighting a deep tank is a common hurdle for aquarists. Light loses intensity as it travels through water, meaning your substrate might not get enough PAR (Photosynthetically Active Radiation) for plants to grow.
If you plan on keeping live plants, look for LED fixtures specifically designed for “high-growth” or deep tanks. High-output LEDs will ensure your ground-cover plants don’t stretch and turn yellow.
Heating and Aeration
Heat rises, so in a tall tank, the top can be warmer than the bottom. I recommend placing your heater horizontally near the bottom or right next to the filter intake to ensure even heat distribution.
Adding a discreet air stone or a sponge filter at the base is a non-negotiable for me. This forces bubbles to travel the entire height of the tank, maximizing gas exchange and keeping your inhabitants breathing easily.
Designing Your 20 Gallon Hexagon Fish Tank
Aquascaping a vertical space requires a different strategy than a traditional layout. You want to lead the eye upward, utilizing the entire water column to create a sense of scale.
When designing your 20 gallon hexagon fish tank, think in terms of layers. You have the foreground (bottom), the mid-ground (center), and the background (the tall vertical space).
Utilizing Hardscape for Height
Don’t be afraid of large pieces of driftwood or rockwork. Manzanita wood or tall pieces of Spider Wood are perfect because their spindly branches can reach toward the surface.
You can also stack Dragon Stone or Seiryu Stone to create “towers.” Just ensure that any tall structures are stable and won’t tip over if a larger fish brushes against them or if you are cleaning the glass.
Selecting the Right Plants
Plants are the secret to a thriving 20 gallon hexagon fish tank. They provide oxygen, absorb nitrates, and give your fish a sense of security in the open water.
- Vallisneria: These are “ribbon” plants that grow very tall and will eventually “carpet” the surface, creating a beautiful jungle look.
- Amazon Swords: A classic choice that grows wide and tall, filling the center of the tank with lush green leaves.
- Java Fern & Anubias: These can be attached to your driftwood at different heights, creating “islands” of green throughout the water column.
Substrate Choices
For a 20-gallon setup, I prefer a nutrient-rich soil capped with fine gravel or sand. This provides the best of both worlds: nutrients for the roots and a clean, aesthetic look for the viewer.
If you are keeping shrimp, a dark substrate like Fluval Stratum or black sand will make their colors “pop” against the green plants. It also helps the fish feel more secure than a bright, reflective white sand.
Best Fish and Inhabitants for a Hexagon Setup
Stocking a 20 gallon hexagon fish tank requires a bit of restraint. Since the surface area is smaller, you cannot stock it as heavily as a 20-gallon long tank.
The key is to choose “centerpiece” fish and small schooling fish that don’t require long-distance swimming. Avoid active “sprinters” like Giant Danios or large Rainbowfish.
The Perfect Centerpiece Fish
A single Dwarf Gourami or a pair of Honey Gouramis are excellent choices. They are slow-moving, colorful, and comfortable in the vertical space of a hexagon.
Another fantastic option is a Betta fish. While many people think Bettas only belong in small bowls, a 20-gallon planted hex is a paradise for a long-finned Betta, provided the filter flow is gentle.
Schooling Fish for the Mid-Section
For movement, consider a small school of Neon Tetras, Cardinal Tetras, or Harlequin Rasboras. These fish tend to stay in tight groups and look stunning as they weave through tall plants.
Six to eight of these small characins will fill the mid-water area without overstressing the biological load of the tank. Their bright colors provide a beautiful contrast to the deep greens of an aquascape.
Bottom Dwellers and Cleanup Crew
Because the floor space is limited, I recommend shrimp and snails over larger bottom-dwelling fish. A colony of Cherry Shrimp or Amano Shrimp will work tirelessly to clean up algae.
If you must have a catfish, a small group of Pygmy Corydoras is a better choice than the larger Bronze or Albino varieties. They are tiny, adorable, and will utilize the plants as much as the floor.
Maintenance Challenges and Pro-Tips
Cleaning a 20 gallon hexagon fish tank can be a bit of a reach—literally! Because these tanks are tall, you might find yourself shoulder-deep in water during a gravel vacuuming session.
Invest in a long-handled algae scraper and an extra-long siphon. This will save your arm from getting soaked every time you need to spot-clean the glass or the substrate.
Managing the “Dead Zone”
As mentioned earlier, the corners and the very bottom of a hex tank can become stagnant. During your weekly 25% water change, make sure to siphon the substrate thoroughly.
Pay extra attention to the areas behind your hardscape. Debris tends to collect there, and in a vertical tank, that debris can quickly lead to an ammonia spike if left unchecked.
Testing and Water Chemistry
Because of the lower surface area, keep a close eye on your Nitrate levels. I recommend testing your water once a week using a reliable liquid test kit.
If you notice your fish gasping at the surface, it’s a sign of low oxygen. This is your cue to increase the flow of your air stone or slightly adjust the filter output to create more surface ripples.
Frequently Asked Questions
Can I keep Angelfish in a 20 gallon hexagon fish tank?
While Angelfish love vertical space, a 20-gallon hexagon is generally too small for them as they reach adulthood. They can grow quite large and become aggressive in cramped quarters. It is better to stick to smaller cichlids like Ram Cichlids or Apistogramma.
Is a hexagon tank harder to maintain than a rectangular one?
It isn’t necessarily harder, but it is different. You need longer tools to reach the bottom, and you have to be more diligent about water circulation. Once you have the right equipment, the maintenance schedule is exactly the same as any other tank.
Why is my 20 gallon hexagon fish tank cloudy?
Cloudy water in a new setup is usually a bacterial bloom, which is a normal part of the nitrogen cycle. However, in an established hex tank, it could be a sign of poor circulation. Ensure your filter is rated for at least 100 gallons per hour (GPH) to keep the water turning over.
How many fish can I put in a 20 gallon hex?
A good rule of thumb for this specific shape is to stock lighter than a standard tank. Aim for one centerpiece fish, a school of 6-8 small tetras, and a handful of shrimp. This ensures everyone has enough room and oxygen.
Do I need a special stand for a hexagon tank?
Yes, you should use a stand specifically designed for the hexagon shape. The weight of 20 gallons of water (about 160-200 lbs with substrate) needs to be distributed evenly across all six corners to prevent the glass from cracking or the seals from leaking.
Conclusion: Success with Your Vertical Oasis
The 20 gallon hexagon fish tank is a rewarding challenge for any hobbyist looking to break away from the traditional “box” aquarium. By focusing on vertical aquascaping, choosing the right inhabitants, and ensuring robust filtration, you can create a thriving underwater world.
Remember to prioritize oxygenation and circulation, as these are the most common pitfalls of tall tanks. With a bit of planning and the right tools, your hexagon tank will be the crown jewel of your home.
Whether you are a beginner starting your first tank or an experienced keeper looking for a new project, the hexagon offers a unique perspective on the hobby. Embrace the height, plant heavily, and enjoy the 360-degree beauty of your new aquatic ecosystem!
