You can’t escape the tank debate if you’re in the fishkeeping hobby. Betta fish and tank size go hand in hand. Tank options range from tiny bowls and small tanks of 0.5 to 1 gallon, all the way up to 100+ gallons.
We’ve put this guide together just for people thinking about upgrading to a 20-gallon tank for their betta. It gives you everything you need to set it up right and keep your betta happy and healthy.
Is a 20-Gallon Tank Too Big for a Betta?
A 20-gallon tank is not that big for a betta, It’s actually much closer to the ideal tank size.
Most betta owners hesitate to get or upgrade their tank to a bigger size like 20 gallons. They think that such tanks are too big to handle or maintain. Another misconception is that these tanks are exclusively used for breeding purposes. However, the reality is different from what you might think.
If your betta is living in a small tank, you might be surprised at how much happier and healthier they can be in a bigger space. While bettas are often sold in tiny cups, they thrive best in larger tanks where they have ample room to swim, explore and even coexist with compatible tank mates. A 20-gallon tank isn’t just an upgrade in size, it’s a chance to give your betta a fuller and more active life.
Larger tanks are beneficial and easy to maintain compared to smaller ones. They’re also closer to the ideal size for betta fish. If your space and budget limitations allow you to buy a 20-gallon tank, confidently go with it.
Advantages of 20-Gallon Betta Tank
If you’ve ever heard that a betta can live in a tiny bowl, it’s time to forget that idea. While a 3-gallon tank or smaller may technically be okay, a 20-gallon tank provides your betta with the best quality of life. It’s the perfect choice for your betta fish, offering numerous benefits for their health, behavior and overall well-being. That’s why moving your betta to a bigger tank can be a total game-changer..
Small Tanks Have Big Problems
Smaller tanks such as 2- or 2.5-gallon, or even 3-gallon tanks can quickly become unstable. Water temperature and quality can change rapidly, which stresses your betta. There’s not much room to swim, and waste builds up quickly, meaning you have to clean more often. It’s basically a cramped and stressful setup for your fish.
Bigger Tank Ensures Healthier Fish
In a 20-gallon tank, the water volume is much higher, which means it stays cleaner and more stable for longer. That stability helps reduce stress and illness in bettas. It provides the opportunity for better mental stimulation and exercise for your betta.
It’s like moving from a tiny studio apartment to a spacious home, way better for comfort and well-being.
Ensure Creative Setup
A 20-gallon betta tank provides ample space for your betta and all the inhabitants of the tank, including betta fish mates, plants and decorations. The tank allows you to be more creative in ensuring hiding spots and arranging decorations that turn the tank into paradise.
Maintain Water Quality
A 20-gallon tank effectively dilutes water toxins such as ammonia and nitrite in more water, reducing their buildup. It will also keep you in your comfort zone by demanding less maintenance efforts such as water changes and cleaning the tank.
Plenty of Space for Live Plants
The tank has plenty of space for live plants and they don’t need frequent trimming due to the extra space. Adding live plants helps filter the water and absorb harmful toxins.
Reduce Maintenance Tasks
Surprisingly, bigger tanks are often easier to maintain. The tanks of this size reduce the burden of too much effort in terms of tank maintenance. Water parameters like pH, ammonia and temperature are more stable and change very rarely. That means less stress for your fish and less work for you.
In a well-maintained 20-gallon tank, we perform a 25% water change every 5-6 weeks and the betta thrives happily there.
Enough Space for Tank Mates
In a 20-gallon tank, there’s enough space to carefully introduce compatible tank mates like peaceful snails or small schooling fish. More space means fewer fights and everyone has room to do their own thing.
Allow Aquascaping
If you are interested in aquascaping, it allows you to create the ecosystem of your dreams. Such tanks are not only a favorite for your betta fish but also add extreme delight and beauty to your room.
If you’re serious about your betta health and happiness, a 20-gallon tank is one of the best upgrades you can make for your betta. It gives your pet the space, stability and enrichment they need to thrive, not just survive.
Ideal Tank Dimensions
Tank dimension is an unignorable factor when considering tank size especially when you opt for a bigger tank. Longer tanks are preferable over taller tanks, as the former provides more surface area and swimming space. They also contribute to less hydrostatic pressure on the delicate betta fish.
Long vs Tall Tanks
The longer and shallower tanks align with the betta fish natural habitats, which are shallow ponds and rice paddies. Shallow tanks make it easy for labyrinth species like betta to access the tank surface to breathe air.
Short-finned betta species like plakats or giant bettas face fewer challenges in taller tanks than long-finned bettas. It’s not so that bettas can’t survive in taller tanks at all. They do, but require certain precautionary adjustments.
If you have been gifted with a taller tank or bought one unknowingly, you will need to make certain adjustments to overcome the challenges of taller tanks.
Place broad-leave plants like Anubias, Java ferns or betta hammocks to create resting spots at various levels so bettas can easily access the surface. Opt for those plants that grow taller than broader so that you don’t need frequent trimming. If the plants don’t reach the upper portion, anchor plants to the tank sides or use fake plants. It may help grow plants in the upper areas of the tank.
Best Tank Mates in a 20-Gallon Tank
Setting up a 20-gallon tank for your betta gives you a lot of freedom and you’ve got two cool options. Either go for a solo betta setup or create a peaceful little community. Both have their perks, depending on your fish personality and your own vibe. Let’s discuss what each setup looks like so you can determine what works best for you.
The Betta-Only Setup
If you’re all about giving your betta the spotlight, a betta-only setup is the way to go. With no tank mates around, your betta gets the whole tank to itself. It has lots of room to swim, explore and chill wherever it likes.
This setup is also great for bettas that are on the moody side or tend to get stressed out easily. No need to worry about other fish bothering them and it’s very easy to manage since you’re only focusing on one fish needs. The solo setup is simple, peaceful and perfect for a low-stress setup that suits both you and your betta.
The 20-Gallon Betta Community Setup
Now if you’re thinking about adding more life and activity to your tank, a betta community can be a fun option but it takes a little planning. You can’t just throw in any fish and expect them all to get along. You’ll need to pick tank mates that have calm and easygoing personalities. Fish that nip at fins or act aggressively will stress out your betta and that never ends well.
Size matters too. Tiny fish might end up as a snack and bigger fish could turn into bullies. You also want to make sure any fish you add can handle the same water conditions your betta needs. Parameters like temperature and pH should match.
Remember to skip the hyperactive fish. Constant buzzing around the tank might annoy your betta. It’s also smart to avoid other labyrinth fish or any fish that look like a betta. Bettas can be surprisingly territorial and may view those fish as rivals.
How Many Female Bettas in a 20 Gallon Tank?
In case, you add more female bettas to a 20-gallon tank, you need at least five females so that no single fish becomes target.
A lot of experienced betta keepers believe that keeping one betta per tank is usually best. If you really want to rescue more bettas, you should be ready with separate tanks or at least tank dividers. In case you’re unable to arrange these things, add lots of plants and hiding spots so they don’t see each other all the time. That way, you can keep everyone safe and happy without risking fights or stress.
Adding just one more female betta usually isn’t a good idea. Even if the single fish seems peaceful, bettas even the girls can get really aggressive with each other. A lot of experienced keepers warn that two females can end up fighting, sometimes badly. Either you keep just one, or you go for a proper group of bettas sorority.
A Summarized Table for Betta Tank Mates
For a 20-gallon tank, peaceful betta tank mates include Rummy-nose tetras, Harlequin Rasboras, Corydoras Catfish, Otocinclus Catfish, Amano Shrimp and Mystery Snails. You can get a clearer idea from the given table.
| Species/Type | Key Info | Tips & Notes |
| Rummy-nose Tetras | Calm, colorful schoolers (6–8) | Good with Corys/Loaches. Add 1 snail for variety |
| Harlequin Rasboras | Peaceful mid-swimmers (6–10) | Introduce slowly to manage bioload |
| Corydoras Catfish | Bottom dwellers (6+); | Use soft sand. Not all types like high temps |
| Otocinclus Catfish | Gentle algae eaters (6+) | Needs algae or veggie diet |
| Amano Shrimp | Large, hardy shrimp | Add plants/hardscape. Doesn’t breed in freshwater |
| Mystery Snails | Low maintenance, peaceful | 1 per tank, avoid overfeeding |
| Avoid These | Long-finned or aggressive fish | No guppies, angelfish or hyperactive species |
Most Recommended 20 Gallon Betta Fish Tanks
GloFish 20 Gallon Aquarium Kit
(View it here on Amazon)
I recently tested the GloFish 20-Gallon Aquarium Kit and it’s a decent setup for beginners. The tank feels well-built with no leaks or cracks and the design is pretty eye-catching. The LED lights are a nice touch especially the blue GloFish setting, which really makes the colors pop.
It also comes with a basic heater that kept the water around 78°F while my room stayed at 70°F, which worked well for my betta. I liked that it includes starter accessories like gravel and fake plants, nothing fancy but enough to get you going.
Now for the downsides. The filter felt underpowered for a 20-gallon tank and the intake tube was too short to reach the bottom, so I had to add an extension. The heater isn’t adjustable, which could be an issue in colder rooms. Also, the plastic lid is pretty flimsy, mine cracked a bit just during setup.
So overall, it’s a solid kit for casual setups but you might want to upgrade a few parts if you’re aiming for a long-term or more advanced tank.
Tetra Color Fusion Aquarium 20 Gallon Fish Tank Kit
(View it here on Amazon)
I haven’t tested the Tetra Color Fusion 20-Gallon Kit myself but based on what a lot of fishkeepers say, it’s a fun and easy setup for beginners. The tank looks great with its color-changing lights and it usually arrives in good shape. It also comes with some starter decorations, so setting it up is pretty simple. The tank is great for kids or anyone just getting into the hobby.
On the flip side, the filter seems to be a common complaint. People say it’s noisy, not very reliable and kind of a hassle to clean. The lid is also pretty flimsy and can crack easily. Plus, the lighting isn’t strong enough for live plants and the accessories aren’t that much durable.
20-Gallon Betta Tank Setup
As a beginner, you might be perplexed by the long 20-gallon betta tank setup. However, the bigger the tank, the easier it is to set up.
Clean the Tank First
Before you do anything, rinse out the tank using just water, no soap and chemicals. Even if it looks clean, this step is essential to remove dust or factory residue.
Find the Right Spot
Select a flat and sturdy surface that can hold the weight of the tank when it is full. Keep it away from windows to avoid direct sunlight and algae, and away from vents or drafts so the temperature stays stable. Also, make sure there’s an outlet nearby for your equipment.
Add and Rinse the Substrate
Find a soft substrate such as sand or smooth gravel. Rinse it well under running water until the water runs clear. This removes dust that can cloud your tank. Then, add a layer to the bottom of the tank, about 1–2 inches thick.
Set up the Decor and Plants
Now comes the fun part, decorating. Start with your hardscapes such as driftwood and rocks. Place them in a way that creates hiding spots and calm areas.
Next, plant your live plants or place artificial ones. Make sure your betta has places to rest near the top such as broad-leaf plants and caves or covered areas to hide when they need quiet time.
Install Your Equipment
Place the filter on one side of the tank and ensure the intake and outflow are functioning properly. A sponge filter or baffled filter is great for low flow.
Install the heater and set it to 78–80°F, ideally near the filter return, so the warm water circulates evenly. Then, secure the light fixture on top.
If you’re not sure which one to pick, take a look at our simple guides on betta heaters, filters, and aquarium lighting. They’ll help you choose what’s best.
Add Water
Use dechlorinated water. you can add a water conditioner to tap water. Fill the tank slowly by pouring water over a plate or plastic bag to keep the substrate and plants from being disturbed.
- Now, allow the tank to cycle for 2–4 weeks to establish beneficial bacteria.
- Pass the water from testing its parameters to ensure ammonia and nitrite are at 0 ppm.
- Once cycled, acclimate the betta by floating its container in the tank and gradually mixing water before releasing it.
The rest is taking care of your tank, for which you can visit our article about betta fish care.
Nitrogen Cycle
The nitrogen cycle keeps your betta safe by breaking down fish waste. First, waste turns into ammonia (toxic), then into nitrite (still harmful) and finally into nitrate (less harmful). Good bacteria handle this whole process.
The best way to cycle your tank is the fishless method. Add a small ammonia source like fish food or pure ammonia and test the water regularly. It usually takes 4–6 weeks.
Avoid cycling with your betta in the tank. Ammonia and nitrite can seriously harm or kill it.
Be ensure the water parameters are on the desired level.
- Ammonia & Nitrite: Should be 0 after cycling
- Nitrate: Keep it under 20 ppm
- pH & Temp: Stay steady (pH 6.5–7.5, Temp 76–82°F)
Cycling may take time, but it’s vital for your betta health.
My Personal Tank Layout
A good layout helps your betta feel relaxed and happy. It’s not just about what looks good. It’s about making sure your fish has calm spaces, fun areas to explore and safe places to hide.
The layout strategy I usually follow:
- Filter on the left, baffled for gentle flow
- Dense plants in the back corners
- Rocks and decor forming a cave in one section
- An open swimming area in the middle
- Floating plants or leaves such as leaf hammock near the top
The point is to include a mix of open swimming space, dense plant cover and some caves or tunnels. This keeps them curious and makes them feel safe.
Betta Fish Care in a 20-Gallon Tank
Taking care of your betta in a spacious 20-gallon setup can be both easy and enjoyable when you maintain a regular routine. We ensure the following ways to keep things under control.
Feeding
Feed your betta a top-notch pellet made just for them. Every now and then, treat them to frozen or live foods such as brine shrimp, mosquito larvae, bloodworms or daphnia.
If you’ve got a community tank, feeding needs a little planning to ensure every fish gets enough food. Some fish eat other fish while others are slow, so keep an eye on that. Take care of the following things in a community tank.
- Identify the specific dietary needs of each species in your tank.
- If you’re unsure about proper betta food, choose a combination of pellets, frozen foods or live foods.
- Use sinking pellets or wafers for tank mates like kuhli loaches or corydoras.
- Follow a proper feeding schedule.
- Try feeding in different spots or at different times if needed.
- Remove the uneaten, leftover food in the tank using a siphon or net.
- If your betta eats food meant for other tank mates, separate the betta in the breeder box during feeding.
Add Live Plants
Adding live plants to a betta tank is essential. A heavily planted tank mimics a natural habitat and oxygenates it. An unenriched tank from the inside can stress your betta or tank mates. The most recommended aquarium plants for 20-gallon betta tank are Anubias, Java Ferns, Amazon Sword and Hornwort.
Whatever plants you choose for your tank, ensure the following conditions to promote plant growth.
- Low to moderate-lighting plants as the high-light-demanding plants can promote algae growth.
- Nutrient-rich substrate to help the rooted plants thrive.
- Low-maintenance plants that don’t require CO2 injection.
Water Treatment
Once a week, change about 25% of the water. Make sure the new water is at the same temperature as the tank and always use a dechlorinator.
While you’re at it, test your water for ammonia, nitrites, nitrates and pH. Just to be sure everything is on track.
Monthly Deep Clean
Perform a light vacuuming of the substrate to remove any leftover debris. There is no need to go too deep.
If your filter flow seems weaker, gently rinse the filter media in a bowl of old tank water. Never use tap water as it can kill the helpful bacteria living in the filter. It’s also a good time to wipe off any algae from the glass and decorations.
Always keep an eye out for anything unusual. If your betta is not eating, looking droopy, clamping their fins or losing colors, it could be a sign of stress or illness.
Daily Observations
Every day, take a quick look at how your betta’s doing. Are they swimming around okay? Eating well? Do their fins and body look normal?
Also, ensure your heater is functioning properly and the water is at the correct temperature of 78-80°F.
Transition Challenges
Older bettas transitioning from smaller tanks to larger ones may experience temporary stress or depression due to the unfamiliar environment. Acclimate the betta when adding it to a new tank. Add a small amount of clean water from the old tank to the new one to make it familiar. Similarly, provide consistent hiding spots and plants to help them adjust.
