10 Best Freshwater Fish 20-gallon Tanks [2025]
This post contains affiliate links. As an Amazon Associate, we earn from qualifying purchases.
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
- GLASS AQUARIUM KIT: The kit includes one glass aquarium with a low-profile, hinged hood, an LED lighting system, an internal filter and filter cartridge, an aquarium heater and thermometer, a water conditioner sample
- LED LIGHTING: Energy-efficient LEDs give you a beautiful natural daylight effect.
- FILTRATION SYSTEM: The included Tetra Internal Filtration System features mechanical filtration to catch debris and chemical filtration with Ultra-Activated Carbon for removal of odors, discoloration and toxins.
- EASY SETUP: Aquarium kit includes items you need to create a healthy home for your fish*.
- SIZE: This 20-gallon glass aquarium measures 24 inches wide by 12 inches deep by 16 inches high
- ★100W aquarium heater is suitable for 10 to 20 gallons aquariums,Length - 9",voltage 110-120V, power cord is 6ft, please choose the right wattage aquarium heater according to our size chart.
- ★It shows an area to adjust the temperature. It's not exactly accurate but it turns easy and can be adjusted at small intervals
- ★Explosion Proof: 2mm thickened quartz glass,can be used in fresh water and salt water aquariums,easy to hide in the tank.
- ★Precise temperature dial from 68 to 89°F allows for complete control of aquatic climate within a 1-degree difference.
- ★Adjustable Aquarium Fish Tank Water Heater Sensitive and reliable thermostat maintains uniform temperature. Automatic shut off when the temperature is reached
- 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
- GLASS AQUARIUM KIT: The starter kit includes one glass aquarium with a low-profile hinged hood an LED lighting system an internal filter and filter cartridge an aquarium heater and thermometer a water conditioner sample.
- LED LIGHTING: Energy-efficient LEDs give you a beautiful natural daylight effect.
- FILTRATION SYSTEM: The included Tetra Internal Filtration System features mechanical filtration to catch debris and chemical filtration with Ultra-Activated Carbon for removal of odors, discoloration and toxins.
- EASY SETUP: Aquarium kit includes items you need to create a healthy home for your fish.
- SIZE: This 20-gallon glass aquarium measures 24 inches wide by 12 inches deep by 16 inches high.
- 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.
- Contains one (1) API TAP WATER CONDITIONER Aquarium Water Conditioner 16-Ounce Bottle
- Neutralizes chlorine, chloramines and other chemicals to make tap water safe for fish
- Prevents tap water chemicals from causing gill destruction, tissue irritation and fish death
- Super strength, high concentration formula
- Use when adding or changing water and when adding new fish to freshwater and saltwater aquariums
- 【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
- 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
- Stylish Fluval Aquarium: Contemporary design with curved front and honeycomb wrap that conceals water line and filter compartment sides
- Customizable LED Aquarium Lights: Fully adjustable 7500K White + RGB LEDs for endless color blends and plant growth support; FLEXPad remote for special effects like lightning bolts and fading cloud cover
- Powerful Fluval Fish Tank Filtration: 3-stage filtration with oversized mechanical, chemical, and biological media for superior water quality
- Perfect Pet Supplies: Fish tank enclosure with multi-directional dual outputs for customized water flow; easy feed top cover opening
- Innovation for Fish Keepers: Fluval innovates to foster a sustainable future where aquatic life and humankind can thrive in harmony
- 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.
