20 Gallon Hexagon Fish Tank Lid – The Ultimate Guide To Finding The Right Fit

Finding a high-quality 20 gallon hexagon fish tank lid can feel like searching for a needle in a haystack.

Most aquarium shops stock rectangular covers by the dozens, but the unique geometry of a hexagon tank often leaves hobbyists frustrated and searching for custom solutions.

If you are struggling with excessive evaporation or worrying about your prize Betta jumping out, you are in the right place.

In this guide, I will walk you through the best retail options, DIY hacks, and essential measurements to ensure your aquatic friends stay safe and your water stays crystal clear.

Why a 20 Gallon Hexagon Fish Tank Lid is Essential for Your Setup

Many new keepers underestimate the importance of a solid cover, thinking it is just an aesthetic choice.

In reality, a 20 gallon hexagon fish tank lid serves as the primary line of defense for your ecosystem.

Hexagon tanks are taller than they are wide, which creates a unique set of challenges for temperature regulation and gas exchange.

Preventing the “Great Escape”

Many popular fish species, such as Hatchetfish, Bettas, and even some shrimp, are notorious jumpers.

Without a secure lid, a sudden shadow or a splash during feeding can startle them right over the glass edge.

A well-fitted lid ensures that your livestock stays exactly where they belong—inside the water.

Managing Evaporation and Humidity

Because hexagon tanks have a smaller surface area relative to their volume, they can suffer from localized humidity issues.

A lid helps trap moisture, preventing your living room from becoming a sauna while keeping your water parameters stable.

When water evaporates, it leaves behind minerals, which can lead to “old tank syndrome” if you aren’t careful with your top-offs.

Light Mounting and Safety

Most modern LED lighting systems require a flat, stable surface for mounting or sitting.

A sturdy lid provides the necessary support for your full-spectrum lights, ensuring they don’t accidentally fall into the water.

Water and electricity are a dangerous mix, so a physical barrier is a non-negotiable safety feature for any home aquarium.

Measuring Your Hexagon Tank Like a Pro

Before you click “buy” on a 20 gallon hexagon fish tank lid, you must understand that not all 20-gallon hex tanks are created equal.

Brands like Top Fin, Marineland, and Aqueon often have slightly different dimensions for their “standard” sizes.

Getting your measurements wrong by even a quarter-inch can result in a lid that slides around or fails to sit flush.

Point-to-Point vs. Flat-to-Flat

When measuring a hexagon, you need two primary numbers to confirm the fit.

First, measure “flat-to-flat,” which is the distance from the center of one flat side to the center of the opposite flat side.

Second, measure “point-to-point,” which is the distance from one corner across the center of the tank to the opposite corner.

Checking the Inner Rim

Most glass or plastic lids sit on a small plastic lip inside the tank’s top frame.

Use a flexible measuring tape to measure the inside dimensions of this rim.

This ensures that the lid you choose will sit securely without falling into the tank or protruding over the edges.

Top Material Choices for Your Hexagon Cover

When selecting a 20 gallon hexagon fish tank lid, the material you choose will impact your light penetration and maintenance routine.

Each material has its own set of pros and cons that you should consider based on your specific inhabitants.

Tempered Glass Lids

Glass is the gold standard for most aquarists because it does not warp over time.

It provides excellent clarity for your lights, allowing PAR levels to remain high for your aquatic plants.

Look for glass lids with a back plastic strip that can be cut to accommodate your hang-on-back (HOB) filter or heater cords.

Acrylic and Polycarbonate

Acrylic is lightweight and impact-resistant, making it a “shatter-proof” alternative to glass.

However, cheap acrylic is prone to bowing or “cupping” due to the moisture on one side and the heat from the lights on the other.

If you go the plastic route, I highly recommend multi-wall polycarbonate or thick Lexan, as these materials resist warping much better than standard hobby-store acrylic.

Screen and Mesh Covers

If you are keeping high-energy fish but don’t have a major evaporation problem, a mesh lid is a fantastic choice.

Mesh allows for maximum gas exchange, which is vital for keeping oxygen levels high in a tall hexagon tank.

These are often DIY projects using a window screen frame kit and clear bird netting or specialized aquarium mesh.

Where to Buy a 20 Gallon Hexagon Fish Tank Lid

Finding a pre-made 20 gallon hexagon fish tank lid in a local pet store is increasingly difficult.

Most manufacturers sell these as part of a complete kit, and they rarely sell the lids as standalone replacement parts.

However, there are a few reliable avenues you can explore to find a replacement.

Specialized Online Retailers

Websites like Amazon, Chewy, and Petco occasionally stock the Marineland or Aqueon branded hexagon glass tops.

Always check the product reviews to see if other owners of your specific tank brand found them to fit correctly.

Common dimensions for these lids usually hover around the 18-inch mark from point to point, but always double-check your own measurements.

Local Glass Shops

One of my favorite “pro tips” for hexagon owners is to visit a local glass cutting shop.

You can bring them a cardboard template of your tank’s opening, and they can cut a piece of 1/4-inch tempered glass to fit perfectly.

This is often cheaper than buying a branded lid and results in a much higher-quality product with polished edges.

DIY: How to Make Your Own Custom Hexagon Lid

If you enjoy a bit of weekend crafting, building your own 20 gallon hexagon fish tank lid is a rewarding project.

This allows you to customize the cutouts for your specific equipment, such as surface skimmers or auto-feeders.

The Polycarbonate Method

Polycarbonate is incredibly easy to work with using standard household tools.

1. Create a cardboard template that fits perfectly inside your tank’s rim.
2. Trace the template onto a sheet of UV-resistant polycarbonate.
3. Cut the shape using a jigsaw with a fine-toothed blade or a heavy-duty utility knife.
4. Sand the edges smooth to prevent any scratches to your tank or your hands.

The Screen Frame Method

For those who want a “breathable” lid, a screen frame is the way to go.

You can buy a screen frame kit from a hardware store and use a hacksaw to cut the pieces to match the six sides of your tank.

Use plastic corner connectors (which may need to be slightly filed to fit the 120-degree angles of a hexagon) to join the frame.

Finish it off by splashing some clear monofilament netting across the frame for a nearly invisible look.

Lighting and Ventilation Considerations

A lid is more than just a topper; it is an integral part of your tank’s life support system.

When you install your cover, you must ensure that you aren’t accidentally suffocating your fish or overheating your water.

Airflow Gaps

Never seal your tank completely airtight; your fish need oxygen exchange at the surface.

Ensure there is at least a small gap near the filter or a few drilled holes in a plastic lid to allow CO2 to escape and O2 to enter.

If you notice your fish gasping at the surface, your lid might be restricting airflow too much.

Heat Dissipation

High-output LED lights generate a significant amount of heat on their underside.

If your lid is sitting directly against the light, it can trap that heat, causing your water temperature to spike.

Use risers or mounting legs to keep a small space between the lid and the light fixture to allow for heat dissipation.

Maintaining and Cleaning Your Aquarium Lid

Over time, your lid will inevitably become covered in hard water stains and algae.

This “crust” doesn’t just look bad; it actually blocks the light spectrum that your plants and corals need to thrive.

Removing Calcium Buildup

To clean a glass lid, avoid using Windex or other household chemicals, as the fumes can be toxic to your fish.

Instead, use a mixture of white vinegar and distilled water.

Soak a paper towel in the solution, lay it over the calcium deposits for ten minutes, and the white crust should scrub right off with a non-abrasive pad.

Preventing Scratches

If you have an acrylic or polycarbonate lid, be very careful when cleaning.

Even a paper towel can leave fine scratches that turn the plastic “cloudy” over time.

Use a soft microfiber cloth and specifically formulated acrylic cleaners to maintain that “invisible” look.

Frequently Asked Questions (FAQ)

Can I use a regular 20-gallon lid on a hexagon tank?

No, a standard 20-gallon tank is rectangular (usually 24″ x 12″), whereas a hexagon tank has six equal sides. The shapes are fundamentally different and are not interchangeable.

Why is my 20 gallon hexagon fish tank lid warping?

Warping usually happens with thin acrylic lids. The side facing the water absorbs moisture and expands, while the side facing the light dries out and shrinks. Switching to glass or thicker polycarbonate will solve this.

How do I feed my fish without taking the whole lid off?

Most glass lids come with a plastic “hinge” in the middle. If you are building a DIY lid, you can cut a small 2-inch triangle off one of the corners to act as a permanent feeding hole.

Will a lid affect my aquarium plants?

A clean glass lid has a negligible effect on light penetration. However, a dirty or salt-crested lid can reduce light by up to 30%. Regular cleaning is key for a high-tech planted tank.

Are there mesh lids available for hexagon tanks?

Pre-made mesh lids for hexagons are rare. Your best bet is to use a DIY screen kit or look for custom 3D-printed lid clips that hold a mesh net in place.

Conclusion: Securing Your Hexagonal Oasis

Choosing or building the right 20 gallon hexagon fish tank lid is one of the best investments you can make for your hobby.

It provides peace of mind, knowing your fish are safe, and it significantly reduces the time you spend topping off evaporated water.

Whether you decide to order a custom glass top or embark on a DIY polycarbonate project, the key is accuracy in your measurements.

Take your time, measure twice, and enjoy the beautiful, unobstructed view of your unique hexagon aquarium.

Don’t let the odd shape of your tank discourage you—with a little effort, you can have a professional-looking setup that keeps your aquatic ecosystem thriving for years to come!