10 Best Freshwater Fish For 20-gallon Aquariums [2025]
This post contains affiliate links. As an Amazon Associate, we earn from qualifying purchases.
Choosing the best freshwater fish for 20-gallon aquariums can be a daunting task, as the sheer variety of species available makes it challenging to find the perfect fit for your specific needs. To simplify this process, we have carefully shortlisted ten top products based on factors such as compatibility, care requirements, and color variety. Our curated list not only saves you time but also alleviates the hassle of extensive research, ensuring you can confidently select the ideal fish for your aquarium.
Top 10 Freshwater Fish For 20-gallon Aquariums In The Market
Freshwater Fish For 20-gallon Aquariums 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
- 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
- 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
- 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.
- 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.
- 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
- INCLUDES CARTRIDGE: The molded ribbed back maximizes contact with water – includes premium activated carbon.
- BIOLOGICAL FILTRATION: Bio-Foam biological filtration removes toxic ammonia and nitrites on contact.
- QUIET: Decoupled motor with dampeners reduces noise to below 40 dB.
- POWERFUL: Impeller and motor assembly designed for efficient power usage filters 10- to 20-gallon aquariums 5 times per hour.
- SLEEK DESIGN: Designed to fit standard aquarium hoods and canopies, the Aqua-Tech Ultra Quiet Power Filter makes aquatic filtration easy.
- Ultra Quiet Submersible Filter: AQQA Aquarium Sponge Filter is air-powered and ultra-quiet, providing efficient filtration without disturbing your fish; (NEED TO CONNECT AN AIR PUMP to Work, Air pump and air hose are NOT INCLUDED in the package) Please prepare a suitable air pump for this filter according to your tank size.
- Mechanical and Biological Filtration: The sponge filter provides mechanical filtration, the vertical pattern design increases the filtering area and helps to filter efficiently; Bio ceramic media balls provide biological filtration, it helps with decomposing harmful substances and cultivating beneficial nitrifying bacterial at the same time.
- Replaceable Filter Media: The filter sponge and bio ceramic media balls are both replaceable. You can easily remove the sponge from the filter for cleaning or replacement. (2 sponges in the package in total) The bio cermaic balls are also washable and reusable, or you can change them with other filter media as you demand.
- Multi-functional Aquarium Filter: The fish tank sponge filter combines filtration, aeration and water circulation in one, helping to keep your fish tank crystal clean and provide an excellent living environment for your aquarium inhabitants.
- Wide Application: AQQA sponge filter can work great in breeding fry tank, shrimp and betta fish tank, freshwater and marine tank. Small filter is suitable for 5-20 gallon tank, medium filter is suitable for 20-110 gallon tank. Please squeeze the sponge repeatedly until the sponge is full of water, so that the filter can sink on the bottom of the aquarium.
- 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.
- 【200 Watts Aquarium Heater】: This 100W aquarium heater is ideal for 20 to 40-gallon saltwater or freshwater aquariums. It measures 8.3 inches in length, operates on 110-120V, and comes with a 6.6-foot power cord. Please refer to our size chart to choose the correct wattage for your aquarium.
- 【Overheating & Off-Water Protection】: The heater automatically shuts off and stops heating when the water temperature exceeds the preset level or if it becomes exposed to air. It will display an error code until the temperature drops below the preset limit or the heater is fully submerged again. Error codes: E1 – out of water; E2 – mechanical failure. This multi-layer protection ensures you never have to worry about "boiled fish"!
- 【Digital LED Controller】: Adjustable temperature range: 64℉-95℉, with an accuracy of ±1°F, you can easily adjust the temperature using the external controller without touching the water. The LED screen displays the current water temperature, preset temperature, and an auto shut-off warning. It's simple and user-friendly!
- 【Explosion-Proof Quartz Glass Aquarium Heater】: Made from explosion-proof quartz glass, this submersible heater utilizes high-temperature-resistant nickel-chromium heating wire and quartz sand for efficient heat conduction, providing rapid water heating and long-lasting performance. The durable black housing, crafted from PC material, offers superior heat resistance to regular ABS, protecting your fish, aquatic life, and yourself from burns.
- 【Fully Equipped with Warranty】: This aquarium heater has everything you need: 1 heater, 1 controller, 2 suction cups, 1 complimentary thermometer strip, and 1 instruction manual. It also includes a 12-month warranty for your peace of mind.
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 Freshwater Fish for 20-Gallon Aquariums
1. Tank Size and Stocking Levels
Before purchasing fish, it’s crucial to understand the capacity of your 20-gallon aquarium. A general rule of thumb is one inch of fish per gallon of water, but this can vary based on the species. Some fish require more space due to their activity levels or territorial behavior. Overcrowding can lead to stress, which may cause health problems for your fish.
2. Water Parameters
Different species of freshwater fish thrive in specific water conditions, including pH, temperature, and hardness. You must test your aquarium’s water and ensure it meets the needs of the fish you intend to keep. For example, some species prefer acidic water, while others thrive in alkaline conditions. Researching the ideal water parameters for your chosen species will help ensure a healthy environment.
3. Compatibility of Fish Species
Not all freshwater fish get along with each other. Some species can be aggressive or territorial, while others may be shy and easily stressed. It’s essential to research and choose compatible species to create a harmonious tank environment. Consider factors such as size, temperament, and social behavior when selecting your fish.
4. Filtration and Maintenance
A 20-gallon aquarium requires an efficient filtration system to maintain water quality. Ensure that your filter is suitable for the tank size and has a good flow rate for the species you choose. Regular maintenance, including water changes and filter cleaning, is necessary to keep the tank healthy and provide a suitable environment for your fish.
5. Diet and Feeding
Different species of fish have varying dietary needs. Research the specific feeding requirements for the fish you plan to keep, as some may need specialized food or have particular feeding behaviors. It’s important to provide a balanced diet to promote growth and health, which can differ significantly among species.
6. Aquascaping and Space Considerations
The layout of your aquarium can greatly affect the well-being of your fish. Incorporate plants, rocks, and hiding spots to create a stimulating environment that mimics their natural habitat. This not only provides shelter but can also reduce stress among the fish. Ensure there is enough open swimming space to accommodate the activity levels of your chosen species.
7. Long-term Commitment
Owning fish is a long-term commitment, often lasting several years. Before making a purchase, consider the lifespan of the species you choose and your ability to provide ongoing care. Regular monitoring of health, water quality, and tank conditions is essential for maintaining a thriving aquarium.
FAQs
What types of freshwater fish are suitable for a 20-gallon aquarium?
In a 20-gallon aquarium, you can keep a variety of small to medium-sized freshwater fish. Some popular choices include Neon Tetras, Guppies, Betta fish (one per tank), Corydoras Catfish, Platies, and Zebra Danios. It’s important to consider the adult size of the fish and their compatibility with each other before stocking your tank.
How many fish can I keep in a 20-gallon aquarium?
A common rule of thumb for stocking freshwater fish is one inch of fish per gallon of water. However, this can vary depending on the species and their bioload. For a standard community tank, aim for around 10-12 small fish or a few larger species. Always research the specific needs and behaviors of the fish you plan to keep.
What is the ideal water temperature for freshwater fish in a 20-gallon aquarium?
The ideal water temperature varies by species, but most tropical freshwater fish thrive in temperatures between 74°F and 78°F (23°C and 26°C). It’s important to use a reliable aquarium heater and thermometer to maintain a stable environment for your fish.
How often should I change the water in a 20-gallon aquarium?
It’s recommended to perform partial water changes of about 10-15% weekly or 20-25% every two weeks. Regular water changes help maintain water quality by removing toxins and debris, which is essential for the health of your fish.
What kind of filtration system is best for a 20-gallon aquarium?
A good filtration system is crucial for maintaining water quality in your aquarium. A sponge filter, hang-on back filter, or canister filter can work well for a 20-gallon tank. Choose a filter that has an appropriate flow rate for your tank size and is suitable for the type of fish you are keeping.
Do I need to cycle my 20-gallon aquarium before adding fish?
Yes, cycling your aquarium is essential to establish beneficial bacteria that break down harmful ammonia and nitrites produced by fish waste. The cycling process typically takes 4 to 6 weeks, and you can monitor progress using water test kits. You can cycle your tank using fish, fish food, or a bacterial starter.
What plants are suitable for a 20-gallon freshwater aquarium?
Live plants can enhance the beauty of your aquarium and provide hiding spots for fish. Suitable plants for a 20-gallon tank include Java Fern, Anubias, Amazon Sword, and Cryptocoryne. Ensure that the plants you choose are compatible with the fish species in your tank and consider their lighting and substrate needs.
Can I keep a Betta fish in a 20-gallon aquarium?
Yes, a Betta fish can thrive in a 20-gallon aquarium, especially if it is well-planted and has hiding spots. You can keep a Betta with peaceful tank mates like Corydoras or small Tetras, but avoid keeping them with other Betta fish or fin-nipping species. Always monitor interactions to ensure harmony in the tank.
What should I feed my freshwater fish in a 20-gallon aquarium?
Feed your fish a varied diet that includes high-quality flakes, pellets, freeze-dried, or frozen foods. Supplementing with live foods such as brine shrimp or daphnia can enhance their diet. Be cautious not to overfeed; only provide as much food as your fish can consume in a few minutes.
How do I manage algae growth in my 20-gallon aquarium?
To manage algae growth, keep your aquarium clean by performing regular water changes and cleaning the substrate. Reducing the amount of light exposure and avoiding overfeeding can also help. Incorporating algae-eating fish or invertebrates, like Nerite snails or Amano shrimp, can assist in controlling algae naturally.
The Bottom Line
In conclusion, selecting the right fish for your 20-gallon aquarium can significantly enhance your aquatic experience, both visually and environmentally. The ten freshwater fish featured in this article were carefully chosen based on factors such as compatibility, size, temperament, and overall care requirements. Each species listed not only thrives in a 20-gallon setting but also contributes to a balanced and harmonious ecosystem, making them ideal choices for both beginners and seasoned aquarists alike.
By following our curated list, you can simplify the process of stocking your aquarium, ensuring that you create a vibrant and healthy aquatic habitat. These fish are not just aesthetically pleasing but also relatively easy to care for, which will allow you to enjoy the beauty of your aquarium without the stress of managing incompatible species. Whether you’re looking to start a community tank or add to an existing setup, our recommendations will help you make informed decisions that lead to a thriving underwater world.
