10 Best Freshwater Fish 20-gallon Tanks [2025]
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Finding the best freshwater fish for a 20-gallon tank can be challenging, especially with the vast array of options available on the market. Choosing the right species requires careful consideration of factors such as compatibility, size, and care needs, making the process overwhelming for many aquarists. To simplify your search, we have meticulously shortlisted 10 top products based on expert recommendations and user reviews. Our curated list not only highlights the best options but also saves you valuable time and hassle, ensuring you can create a thriving aquatic environment with ease.
Top 10 Freshwater Fish 20-gallon Tanks In The Market
Freshwater Fish 20-gallon Tanks Review
- Tetra Glass Aquariums are made in the USA and are built to last with scratch resistant glass
- The Tetra Aquarium comes loaded with an LED hood, that provides a natural daytime effect and a Whisper Filter that is whisper quiet while providing powerful, dependable water flow
- Artificial Plants add a unique, natural ocean feel while giving your fish a place to hide which reduces fish stress
- The Tetra Kit includes: one 20 Gallon Glass Aquarium, one LED hood, one Tetra Mini UL Heater, one Tetra Whisper 20 Filter, one artificial Boxwood Plant Mat, four artificial plants. Add gravel and fish to complete your aquarium
- Aquarium Dimensions: 24.2" L x 12.4" W x 16.7" H
- ALL THE EQUIPMENT NEEDED to get started in one box
- LOW PROFILE HOOD contains vibrant cool white LED lighting to bring your aquatic environment to life
- SMARTCLEAN INTERNAL POWER FILTER, providing quick and easy water changes to help improve water quality.
- PRESET HEATER will keep your aquarium temperature at a constant 78 degrees, appropriate for most tropical fish
- KIT INCLUDES: glass aquarium, low profile LED hood, SmartClean internal power filter size medium, EcoRenew filter cartridge size medium, submersible preset heater 50W, premium fish food sample, water conditioner sample, fish net, thermometer and setup guide
- After-sales service - Fish tank belongs to glass products, there will be bumps during transportation. Receive a broken fish tank, please contact customer service in time to return or exchange.
- 100% HIGH-TRANSPARENT GLASS MATERIAL - The fish tank is indeed made of glass after a 3-meter drop and shatter test. If you think it's not, you can try to break it and we'll replace it for free.
- PLANT LIGHTS - 3 types of LED lights provide photosynthesis for plants, providing more oxygen for your aquarium. Reduce adverse reactions of fish caused by lack of oxygen.
- FISH FAVORITE - You can keep bettas, tropical fish, reef fish, guppies, shrimps, crabs, betas and snails in this 20-gallon box, or use it as a fish breeding box.
- WATER TEMPERATURE DETECTION SYSTEM - The fish tank comes with a water temperature detection system, which can help you detect the water temperature and ensure a good living environment for the fish.
- 100% HIGH-TRANSPARENT GLASS MATERIAL - The fish tank is indeed made of glass after a 3-meter drop and shatter test. If you think it's not, you can try to break it and we'll replace it for free.
- WATER TEMPERATURE DETECTION SYSTEM - The fish tank comes with a water temperature detection system, which can help you detect the water temperature and ensure a good living environment for the fish.
- PLANT LIGHTS - 3 types of LED lights provide photosynthesis for plants, providing more oxygen for your aquarium. Reduce adverse reactions of fish caused by lack of oxygen.
- FISH FAVORITE - You can keep bettas, tropical fish, reef fish, guppies, shrimps, crabs, betas and snails in this 20-gallon box, or use it as a fish breeding box.
- FISH FAVORITE - You can keep fighting fish, tropical fish, reef fish, turtles, peacock fish, shrimp, crabs, fighting fish, and snails in this 20-gallon box, or use it as a box for fish.
- The blue LED light completely transforms your aquarium
- GloFish and fluorescent décor create a colorful, neon display
- GloFish Glass Aquariums are made in the USA and are built to last with scratch resistant glass
- The Tetra GloFish Kit includes: one 20 Gallon Glass Aquarium, one LED hood, one Tetra Mini UL Heater, one Tetra Whisper 20 Filter, one GloFish 13" LED Light Stick, three GloFish Plants, one GloFish Yellow Anemone. Add gravel and fish to complete your aquarium.
- Aquarium Dimensions: 24. 2" L x 12. 4" W x 16. 7" H
- Work best on 10 gallon tanks with 20 inches long; with two extendable brackets, this light also fits for fish tank from18 inch to 24 inch long
- Light body without docking brackets: 17” L x 2.7” W. Tank thickness: No limit to rim size
- Configuration: Total 42 LEDs, 30 pcs 6500K white LED, 6pcs blue LED, 3 pcs pink LED, 3 pcs Green LED
- Mode: all lights on and all lights off; no timer; light brightness is not adjustable
- Super bright and energy efficient LEDs, suitable for all freshwater; NOTE：LIGHT IS NOT WATERPROOF,KEEP THE LIGHT AWAY FROM THE SPLASHING WATER
- Orlushy 150W Aquarium Heater: Orlushy 150W heater can work perfectly in 20-30 gallons tank, suitable for aquariums, fish tanks, betta tanks and turtle tanks. The length of this heater is 5.4 inches, which is more compact in size than original heater, taking up less space and can be easily hidden in the aquarium.
- Safer and More Durable Quartz Glass: This aquarium heater is made of gray quartz glass, which has higher hardness than regular quartz glass, more high-temperature resistant and explosion-proof. This material makes the heater safer and more durable to be used in both freshwater and saltwater, longer service life is provided.
- Rapid Water Heating and Accurate Water Sensor: With uniformly wound premium nickel-chromium wire, heat can rapidly dissipate to a wider area in water, more efficient water heating. Unique water temp sensing system can accurately correct the water temperature in real time at set value, protecting your aquatic lives from fluctuating water temperature. Once the water temperature exceeds 95℉, heater will automatically cut off the power and error code “EE” will be shown, getting your fish rid of the risk of “boiling fish”.
- External Controller with LED Digital Display: External control reduces the risk that water gets in and burn out the heater, greatly improving the safety. Remote control allows you to adjust the heater without being done in water and getting hand wet. The temperature is adjustable ranging from 65℉ to 93℉, and the set value changes 1 ℉ per press. Besides, you can also observe the real-time water temperature from the digital display at any time.
- Free Thermometer and 180 Days Warranty: This fish tank heater comes with one free strip thermometer for better temperature calibrator as well as 180 days warranty that free replacement of heater are provided if any problem occurs to it. If you have any issue with the heater, please feel free to contact us. We would provide a timely after-sale service.
- 【ALL-IN-1 POWERFUL DEVICE】- Green killing, reduce odor, oxygenation, wave making, aqurium water pump & filte. Clears cloudy water, It helps reduces water changes, saves time and costs. You can unplug the air tube as a water pump
- 【KEEP CRYSTAL CLEAR: Keep Crystal Clear】- Stage 1: Swiftly and effectively clear cloudy, odorous, smelly, and milky water. Stage 2: The built-in 254nm U-V light further diminishes odor and eradicates green water
- 【ADJUSTABLE BUBBLES-Gentle for Fish】- Adjustable airflow can meet different air supply needs; IPX8: U-V light housing will not leakage. You can lay down the filter in low water level tanks
- 【EASY TO USE】- Applicable for marine and freshwater tanks, vertical or horizontal use. The lowest water level was 3.5 in. The pump, lamp and sponge can be easily disassembled and assembled. Simple maintenance, housing indicator showing U-V working status
- 【AUTOMATIC-DAILY-CYCLE TIMER】- U-V lamp and pump operate separately. Set its working time to 3/6/12/24 as needed. It will auto-off after working for the correspondingly set duration, and repeat the cycle daily without manual adjustment
- Suitable for large fish tanks: Our fish tank stand is designed for 20-29 gallons of fish tanks, providing stable support and a secure display space. It is also equipped with two additional compartments on the right side, with the bottom compartment capable of holding 5 gallons of small fish tanks, allowing you to create a more diverse aquatic environment. Whether you're raising large ornamental fish or arranging aquatic plants, our stand can meet your needs.
- Convenient storage functionality: first-level compartment on the right side, allowing for easy storage of fish food, nets, disinfectants, water conditioners, and other daily supplies. The cabinets are designed with specific spaces, and removing the compartment allows for accommodating canister filters and CO2 hoses. There is also an opening at the back of the stand. This ensures a tidy and organized environment around your fish tank, making it convenient to access the items you need.
- Strength and stability: Our stand is constructed with high-quality materials, featuring steel pipes and sturdy MDF panels, ensuring a maximum weight capacity of 330 pounds for the tabletop and 150 pounds for the bottom. The robust structure and stable design guarantee the stability of your fish tank, eliminating concerns about wobbling or insecurity. Your fish tank will remain rock solid, allowing you to enjoy your aquatic world with peace of mind.
- Stylish modern design: Our stand showcases a sleek black modern design that complements various home decor styles. It serves not only as a practical fish tank stand but also as an exquisite home decoration, adding a touch of modern elegance to your living space. Stand dimensions: 31.49" L*15.74" W*31.49" H TIP: Fish tank not included.
- after-sales service: If you encounter any issues, please feel free to contact us through Amazon, and we will provide a satisfactory solution to meet your needs.
- CRYSTAL CLEAR - Turns CLOUDY and GREEN water crystal clear in 3-7 days. The larger the fish tank, the longer it takes. Reduce the number of water changes in the fish tank.
- DOUBLE FILTRATION - First stage Biochemical Sponge Filter. Second stage 254nm wavelength U-V Light.
- SEPARATE SWITCHES - Control the water pump and fish tank light separately. When you only want to use the aquarium filter function, you can turn off the fish tank U-V light separately.
- SMELLS FRESH - Once the fish tank is full of green will be accompanied by the smell. This green killing machine can reduce the unpleasant smell in the fish tank.
- EASY TO CHECK LIGHT UP - You can easily check that the light is on from the outside of the machine, don't need to take the machine apart to see it.
Our Review Process
To ensure you get reliable product recommendations, we follow a detailed review methodology that includes:
- Market Research: Scanning best-selling and trending products in this category.
- User Feedback: Reviewing customer reviews, star ratings, and complaints.
- Hands-On Testing: Trying select products ourselves when feasible.
- Feature Comparison: Evaluating specs, durability, pricing, and safety.
- Expert Opinions: Consulting with niche experts or credible reviewers.
We independently select the top 10 options based on value, quality, and usability. To learn more, visit our detailed review process.
Key Considerations Before Buying a Freshwater Fish 20-Gallon Tank
1. Type of Fish
Before purchasing a 20-gallon tank, it’s essential to decide what type of freshwater fish you want to keep. Different species have different space, temperature, and water quality requirements. Some fish are more aggressive and territorial, requiring more space, while others are peaceful and can thrive in a community tank. Research the species you are interested in to ensure they are compatible with each other and suitable for a 20-gallon environment.
2. Tank Dimensions and Space
The physical dimensions of the tank should be considered, as a 20-gallon tank can come in various shapes, such as long or tall. The footprint of the tank will affect the number of fish you can comfortably keep and their swimming behavior. Ensure you have enough space in your home for the tank, including consideration for the stand and any equipment you may need.
3. Filtration System
A reliable filtration system is crucial for maintaining a healthy aquarium environment. For a 20-gallon tank, a filter rated for at least 20 gallons is necessary to ensure optimal water quality. Consider whether you want a hang-on-back filter, a canister filter, or a sponge filter, and research the maintenance requirements for each type.
4. Heating Requirements
Maintaining the right temperature is vital for the health of your fish. Most tropical freshwater fish require water temperatures between 75°F and 80°F. A reliable aquarium heater is essential for a 20-gallon tank, especially if you plan to keep species that are sensitive to temperature fluctuations. Make sure to choose a heater that is appropriate for the size of your tank and has a reliable thermostat feature.
5. Aquascaping and Decor
The arrangement of plants, rocks, and other decorations in the tank can influence both the aesthetics and the well-being of the fish. Live plants can help improve water quality and provide hiding spots for shy fish. Be mindful of the type of decor you choose, ensuring it is safe for your fish and doesn’t have sharp edges that could harm them.
6. Water Quality Management
Regular testing and management of water parameters such as pH, ammonia, nitrites, and nitrates are essential for a successful aquarium. Invest in a good water testing kit and familiarize yourself with the ideal water conditions for your chosen fish species. Additionally, consider the type of water (tap, distilled, or RO) you will use and how to treat it for optimal fish health.
7. Budget Considerations
Setting up a 20-gallon freshwater tank involves more than just the cost of the tank itself. Factor in expenses such as the filtration system, heater, substrate, plants, decorations, food, and water treatments. Additionally, consider ongoing costs for electricity, water changes, and maintenance supplies. Make sure to budget for both initial setup and long-term care.
8. Cycling the Tank
Before adding fish to your new tank, it’s crucial to cycle it to establish beneficial bacteria that break down harmful ammonia and nitrites. This process can take several weeks, so plan accordingly. Learn about different cycling methods (fishless cycling is often recommended for beginners) and be patient during this critical step.
9. Maintenance and Time Commitment
Owning a freshwater fish tank requires a commitment to regular maintenance, including water changes, cleaning, and monitoring fish health. Assess your schedule and ensure you have the time to perform these tasks consistently. Regular maintenance not only keeps your aquarium looking great but also ensures the health and well-being of your fish.
FAQs
What types of freshwater fish can I keep in a 20-gallon tank?
In a 20-gallon tank, you can keep a variety of freshwater fish such as bettas, guppies, tetras, rasboras, dwarf cichlids, and small catfish like Corydoras. It’s important to consider the adult size of the fish and their compatibility with each other when planning your tank.
How many fish can I put in a 20-gallon freshwater tank?
A general rule of thumb is to allow 1 inch of fish per gallon of water. For a 20-gallon tank, this means you could typically house around 10-20 inches of fish, depending on the species. However, it’s best to research each species’ specific requirements and consider factors like filtration, tank mates, and water quality.
What kind of filtration is best for a 20-gallon tank?
A good filter is crucial for maintaining water quality in a 20-gallon tank. A hang-on-back (HOB) filter or a sponge filter are both effective options. Look for a filter that provides at least 5-10 times the tank’s volume in gallons per hour (GPH) to ensure proper circulation and filtration.
How often should I change the water in my 20-gallon tank?
It’s recommended to perform partial water changes of about 15-20% weekly to maintain water quality and remove toxins. Regular testing for ammonia, nitrites, and nitrates can help determine when you need to change the water more frequently.
What substrate is best for a 20-gallon freshwater tank?
The best substrate depends on the type of fish and plants you have. For a planted tank, a nutrient-rich substrate or fine gravel is ideal. For a tank with fish that like to dig, such as cichlids, you may want to use sand. Always consider the needs of your specific fish and plants when selecting substrate.
Do I need to add a heater for my 20-gallon tank?
Whether you need a heater depends on the species of fish you plan to keep. Tropical fish generally require a heater to maintain a stable temperature between 75°F and 80°F. If you are keeping coldwater fish, such as goldfish, a heater may not be necessary.
Can I keep live plants in my 20-gallon tank?
Yes, live plants can enhance the appearance of your tank and provide benefits such as improved water quality and habitat for your fish. Choose low-maintenance plants like Java fern, Anubias, or Cryptocoryne, which thrive in various conditions and can be kept with many freshwater fish species.
How can I cycle my 20-gallon tank?
Cycling your tank involves establishing beneficial bacteria to break down harmful ammonia and nitrites. You can cycle your tank using the fishless method by adding ammonia to the water or by introducing a few hardy fish. Additionally, you can use filter media or substrate from an established tank to speed up the process. The cycling process usually takes 4-6 weeks.
What are some common problems I might encounter with a 20-gallon tank?
Common problems include poor water quality, algae growth, and fish diseases. Regular water testing, consistent maintenance, and monitoring the health of your fish can help prevent these issues. If problems do arise, research the specific issue to find appropriate solutions.
What is the best way to ensure my fish are healthy in a 20-gallon tank?
To ensure your fish remain healthy, maintain good water quality through regular testing and water changes, provide adequate space and compatible tank mates, feed a varied and appropriate diet, and monitor their behavior for signs of stress or illness. Regular tank maintenance and observation are key to a thriving aquarium.
The Bottom Line
In conclusion, selecting the right fish for your 20-gallon freshwater tank can be a rewarding experience that enhances the beauty of your aquatic environment. The ten fish we’ve highlighted in this article have been carefully chosen based on their compatibility, ease of care, and suitability for a smaller tank size. Each species brings its unique charm and characteristics, ensuring that whether you’re a beginner or an experienced aquarist, there’s something here for everyone. Our selection criteria focused on factors such as temperament, tank requirements, and overall health, providing you with a well-rounded list of options to consider.
By following our list, you can create a balanced and harmonious aquarium that thrives over time. Paying attention to the specific needs of each fish and ensuring that their habitats are conducive to their well-being can lead to a vibrant and lively community tank. Remember, a well-maintained aquarium not only benefits the fish but also offers endless enjoyment for you as a hobbyist. Embrace the journey of fishkeeping, and let these selections inspire you to build your perfect underwater oasis.
