For beginners, a 20-gallon aquarium is a great choice. It’s ideal for a wide variety of fish that are easy to care for and grow fast. A 20-gallon aquarium is large enough to keep a wide range of freshwater fish, plants, and invertebrates.
It is a lot of fun to see your fish swimming around your aquarium. But it’s also important to know what kind of fish to choose for 20-gallon tank and how many fish you can keep at once.
This guide introduces you to the best fish for a 20-gallon tank.
How Many Fish you can keep in a 20-Gallon Tank?
There are many fish species that you can keep in a 20-gallon tank. You may decide to keep more than one species if you want to be able to view the different species in the aquarium from time to time.
So, what about the maximum number of fish that you can keep in a 20-gallon tank? The rule of thumb is to allow one inch of fish per gallon of water in the tank. But there are a few other things to think about when stocking your aquarium, we’ll discuss in more detail in this guide.
You should make sure that you don’t keep too many fish in the tank. Overcrowding is a major cause of stress in fish tanks. Stress can lead to illness, disease, and even death.
The biggest fish that you can put in a 20-gallon tank
We usually think that 20-gallons is a very big aquarium. That’s true, but what we need to remember is that the fish needs enough space to swim and to move around. The space they need varies depending on the type of fish.
For example, if you want to keep Roseline Sharks, you must make sure that you have at least 20 gallon tank. This will ensure that they don’t get stressed. Roseline Sharks are excellent swimmers, and you should provide them with plenty of space to swim around.
It is a good idea to keep fish that grow no larger than six inches in a 20-gallon tank. And you need to remember the one inch per gallon rule as a general rule.
What is important when choosing fish for a 20-gallon tank?
Adult size of the fish
Fish that are sold at a pet store are usually juveniles that are less than three inches long. A few fish are sold at the pet store that have grown to be larger than that.
Fish babies grow very quickly. This is why you should do your research before you buy a fish. You may want to ask in pet store about the size of the fish you want to buy.
Compatibility
A fish is a living creature with its own characteristics. It needs to be cared for properly and it should be kept in the right conditions.
In nature, many small fish are schooling species that adopt the strategy of safety in numbers. For that reason, those species must be kept in shoals of at least six individuals to avoid the fish becoming stressed.
If you want a nice tank, you will need to make sure that you have the right kind of fish for it. Some fish are shy and peaceful, while others are aggressive and territorial.
Some fish are very active and like to swim around. They need lots of swimming space to be happy. There are different types of fish that do well in the same environment.
It is important to research different types of fish to figure out what fish will work best for you. You will find out which fish are good companions for each other. It is also a good idea to look into different types of fish before you purchase them.
Water parameters
Water temperature is very important. It can affect your fish’s health.
All types of fish have different preferences when it comes to water parameters.
In order for your fish to live well, you need to provide them with the proper water conditions, such as temperature, pH, and hardness.
Make sure you choose a fish species that shares the same pH, temperature and water hardness requirements.
Tropical and cold-water fish can suffer from temperature shock if the water temperature is either too warm or too cold for them. A good aquarium heater is essential for keeping your tropical fish happy and healthy.
You should make sure that the water is at the right temperature so good quality aquarium thermometer will help you to maintain this temperature. Don’t ever mix tropical species with cold water fish.
Ideas for your 20 gallon harmonious community tank
If you are planning on buying a fish tank, you’ve got a very exciting decision to make. Here’s an idea for a peaceful community tank:
Livebearer Community Tank
- 6 x Guppies
- 2 x Swordtail
- 2 x Mollies
Tetra Community Tank
- 8 x Neon tetras
- 6 x Glowlight tetras
- 3 x Cherry shrimp
Shrimps can be an interesting addition to your aquarium. They are not only colorful, but they can also add a lot of activity to your tank. Some species will eat algae, which can help keep your aquarium clean.
Plants in fish tank
There are several reasons why you should keep plants in your fish tank. Aquatic plant life adds aesthetics to an aquarium. The plants absorb nitrogen and carbon dioxide from the water for use as fertilizer.
Plants can also help to keep your aquarium clean. They help to prevent algae from forming. To make sure that your plants grow well, it is important that you provide them with the right environment.
Many aquarium owners have started with hardy aquatic plants. Aquatic plants are easy to care for and require little maintenance. Once you get the hang of caring for these plants, you will soon see how easy they are to maintain.
There are many excellent beginning plants that grow well in low to medium light conditions. They include: Anubias, Valisneria, Hornwort, Java moss, Marimo moss balls, Amazon sword.
The best fish species for a 20-Gallon Tank
The list of fish and invertebrate that you can keep in 20-gallon fish:
Cardinal Tetra (Paracheirodon axelrodi)
| Common name(s) | Cardinal tetra, red neon tetra, scarlet characin |
| Binomial name | Paracheirodon axelrodi |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range – lenght | 2 inches |
| Water parameters | Temp 73–81°F (23–27°C) pH 4.6–6.2 Hardness Up to 4 dGH |
| Tank level | In the middle and top of the tank |
| Diet | Omnivore |
| Lifespan | Up to 2 years |
| Tank mates | Small tetras with a similar temperament, Pencil fish, Hatchet fish, Rasboras, Dwarf gouramis, Barbs, Corydoras catfish, Freshwater shrimps, crabs, and snails |
Ember Tetra (Hyphessobrycon amandae)
| Common name(s) | Ember Tetra, Fire Tetra |
| Binomial name | Hyphessobrycon amandae |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range – lenght | 0.6–0.8 inch |
| Water parameters | Temp 70 – 84ºF ( 21 – 29ºC) pH 5.8 – 6.8 Hardness < 18 dGH |
| Tank level | In the middle |
| Diet | Omnivore |
| Lifespan | Up to 2 years |
| Tank mates | Small corydoras or other peaceful fish from Characidae family, hatchetfish, dwarf cichlids, rasboras, microrasboras, or neon tetras |
Rosy Tetra (Hyphessobrycon rosaceus)
| Common name(s) | Rosy Tetra, Candy Cane Tetra, Rosy Fin Tetra |
| Binominal name | Hyphessobrycon rosaceus |
| Care Level | Intermediate |
| Temperament | Peaceful |
| Size range –lenght | 1.6 inches |
| Water parameters | Temp 75o to 82o F (23.0 – 27.8 oC) pH 5.5-7.5 Hardness 5-19 dGH |
| Tank level | Middle – Top |
| Diet | Omnivore |
| Lifespan | 3-5 years |
| Tank mates | Corydoras Catfish hatchetfish, small dwarf cichlids such as Apistogramma or Mikrogeophagus, and some of the smaller Loricariidae (suckermouth catfish), White Skirt Tetra, Harlequin Rasbora, Black Widow Tetra, Bleeding Heart Tetra |
Flame Tetra (Hyphessobrycon flammeus)
| Common name(s) | Flame Tetra, Fin tetra, Rio Tetra |
| Binominal name | Hyphessobrycon flammeus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1 inch |
| Water parameters | Temp 72o to 82o F (22-27 o C) pH 5.5 – 7.5 Hardness 3-15 dGH |
| Tank level | All areas |
| Diet | Omnivore |
| Lifespan | 3 – 5 years |
| Tank mates | Other small tetras, like Neon Tetras, as well as Danios, Rasboras, and some bottom dwellers, as long as they are peaceful, livebearers. |
Glowlight Tetra (Hemigrammus erythrozonus)
| Common name(s) | Glowlight Tetra |
| Binominal name | Hemigrammus erythrozonus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.5 inches |
| Water parameters | Temp 74o to 82o F (24-28 o C) pH 5.8 – 7.5 Hardness – up to 15 dGH |
| Tank level | Middle |
| Diet | Omnivore |
| Lifespan | Up to 2 years |
| Tank mates | Cory catfish, Neon tetra, Docile loaches, Gouramis, Barbs, Molly fish |
Lambchop Rasbora (Trigonostigma espei)
| Common name(s) | Lambchop Rasbora, False Harleqiun Rasbora, Narrow Wedge Harlequin, Slim Harlequin |
| Binominal name | Trigonostigma espei |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.2 inches |
| Water parameters | Temp 73o to 80o F (22.8-26.7 o C) pH 6.0-8.0 Hardness 1-15 dGH |
| Tank level | All levels |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Coexist with bettas and different types of tetras, including neon tetras, cardinal tetras, and black phantom tetras, also catfish, Dwarf Cichlids, Livebearers, Loaches, and Snails |
Chili Rasbora (Boraras brigittae)
| Common name(s) | Chili Rasbora, Mosquito Rasbora |
| Binominal name | Boraras brigittae |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 0.8 inches |
| Water parameters | Temp 74o to 82oF (23.3-27.8 o C) pH 4.5-7.5 Hardness 3-8 dGH |
| Tank level | Middle – Top |
| Diet | Omnivore |
| Lifespan | 3 to 4 years |
| Tank mates | Shrimp (cherry, bamboo, ghost) Other small peaceful fish (tetras, micro rasboras, danios) Otocinclus Catfish Dwarf Crayfish (cherry, moss) |
Least Rasbora (Boraras urophthalmoides)
| Common name(s) | Least Rasbora |
| Binominal name | Boraras urophthalmoides, Sparrow Rasbora, Spice Rasbora |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.6 inches |
| Water parameters | Temp 76o to 82o F (24.4-27.8 o C) pH 6.0-7.0 hardness 8-12 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 4 to 8 years |
| Tank mates | Shrimp (cherry, bamboo, ghost), other small peaceful fish (tetras, micro rasboras, danios), Otocinclus Catfish, Dwarf Crayfish |
Harlequin Rasbora (Trigonostigma heteromorpha)
| Common name(s) | Harlequin Rasbora, Red Rasbora, Harlequin Fish, Red Razor |
| Binominal name | Trigonostigma heteromorpha |
| Care Level | Intermediate |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 72o to 80oF (22.2-26.7 o C) pH 5.5-7.0 Hardness 2-15 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 5 to 6 years |
| Tank mates | Shrimp (cherry, bamboo, ghost), other small peaceful fish (tetras, micro rasboras, danios), Otocinclus Catfish, Dwarf Crayfish (cherry, moss), Corydoras, Livebearers, Nerite snails |
Dwarf Rasbora (Boraras maculatus)
| Common name(s) | Dwarf Rasbora, Pygmy Rasbora, Spotted Rasbora, Three Spotted Dwarf Rasbora |
| Binominal name | Boraras maculatus |
| Care Level | Intermediate |
| Temperament | Peaceful |
| Size range –lenght | 1 inch |
| Water parameters | Temp 75o to 79o F (23.9-26.1 o C) pH 4.0-6.5 Hardness 1-5 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Peaceful invertebrates, dwarf shrimp, rosy tetra, guppy, plecos, Corydoras, cardinal tetra, neon tetra, green neon tetra, snails |
Galaxy Rasbora (Microrasboras galaxy)
| Common name(s) | Galaxy Rasbora, Celestial Pearl Danio |
| Binominal name | Microrasboras galaxy |
| Care Level | Intermediate |
| Temperament | Peaceful |
| Size range –lenght | 1 inch |
| Water parameters | Temp 70o to 75o F (22.0-27.0°C) pH 6.5-7.5 Hardness 5-15 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Other danios, Pygmy hatchet fish, Guppies, Molly fish, Cherry shrimp, Amano shrimp, Killifish, Regular, ember, cardinal, or green tetras, Honey or sparkling gourami, Cory catfish, Endler’s livebearer, Kuhli loaches, Snails |
Parrot Platy (Xiphophorus hybrid)
| Common name(s) | Parrot Platy, Coral red, Golden, Mickey Mouse, Red Tuxedo Platy,Variatus Platy etc. |
| Binominal name | Xiphophorus hybrid |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 3 inches |
| Water parameters | Temp 65o to 77o F (18.3-25.0°C) pH 7.0-8.0 Hardness 10-25 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Mollies, Guppies, Small tetras and rasboras, cory catfish, snails, bristlenose plecos, rainbowfish, barbs, gouramis |
Red Platy (Xiphophorus maculatus)
| Common name(s) | Red Platy |
| Binominal name | Xiphophorus maculatus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 65o to 77o F (18.3-25.0°C) pH 7.0-8.0 Hardness 10-25 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 4 years |
| Tank mates | Mollies, guppies, swordtails, tetras, snails, barbs, gouramis, corydoras |
Endler’s Livebearers (Poecilia wingei)
| Common name(s) | Endler’s Livebearers |
| Binominal name | Poecilia wingei |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1 inch |
| Water parameters | Temp 75o to 82oF (23.9-27.8°C) pH 7.0-8.0 Hardness 8-20 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 2 to 3 years |
| Tank mates | Mates of the same species and Cherry barb, Ember tetra, Dwarf gourami, Honey gourami, Neon tetra, White Cloud, Corydoras catfish, Glassfish, Glowlight tetra |
Fancy Guppies (Poecilia reticulata)
| Common name(s) | Fancy Guppies, Million Fish |
| Binominal name | Poecilia reticulata |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2.4 inches |
| Water parameters | Temp 64o to 84o F (18.9-28.9°C) pH 6.7-8.5 Hardness 10-20 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 1 to 3 years |
| Tank mates | Mates of the same species and Cherry barb, Ember tetra, Dwarf gourami, Honey gourami, Neon tetra, White Cloud, Corydoras catfish, Glassfish, Glowlight tetra |
Angel Ram Cichlids (Mikrogeophagus ramirezi)
| Common name(s) | Angel Ram Cichlids |
| Binominal name | Mikrogeophagus ramirezi |
| Care Level | Difficult |
| Temperament | Peaceful |
| Size range –lenght | 3 inches |
| Water parameters | 73o to 80o F (22.2-26.1°C) pH 5.0 – 7.5 Hardness 5-12 dGH |
| Tank level | Bottom – Middle |
| Diet | Omnivore |
| Lifespan | 3 years |
| Tank mates | Angelfish, Bolivian rams, Cardinal tetras, Clown loaches, Corydoras, Discus, Dwarf gouramis, Guppies, Honey Gouramis, Kuhli loaches, Mollies, Neon tetras, Platies, Plecostomus, Rummy nose tetras, Freshwater shrimp, snails, Silver dollars. |
Electric Blue Ram (Mikrogeophagus ramirezi)
| Common name(s) | Electric Blue Ram, Butterfly Chchlid, German BLue Ram, Ramirez’s Dwarf Chichlid, Dwarf Butterfly Chichlid |
| Binominal name | Mikrogeophagus ramirezi |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 3 inches |
| Water parameters | Temp 78o to 85oF (25.6-29.4°C) pH 5.0 – 7.5 Hardness 5-12 |
| Tank level | Bottom – Middle |
| Diet | Omnivore |
| Lifespan | 2 to 4 years |
| Tank mates | Angelfish, Bolivian rams, Cardinal tetras, Clown loaches, Corydoras, Discus, Dwarf gouramis, Guppies, Honey Gouramis, Kuhli loaches, Mollies, Neon tetras, Platies, Plecostomus, Rummy nose tetras, Freshwater shrimp, snails, Silver dollars |
Yellow Dwarf Cichlid (Apistogramma borellii)
| Common name(s) | Yellow Dwarf Cichlid |
| Binominal name | Apistogramma borellii |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2.8 inches |
| Water parameters | Temp 78o to 84o F (25.0-28.0°C) pH 5.0-7.0 Hardness 2-15 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 2 to 3 years |
| Tank mates | Neon tetras, Cardinal tetras, Rummynose, Lemon tetras, Hatchetfish, Pencilfish, Small Rasboras (such as Galaxy Rasbora), Pygmy Gouramis, Pygmy Corydoras, Otocinclus Catfish, Corydoras Catfish |
Marlier’s Julie ( Julidochromis marlieri)
| Common name(s) | Chequered Julie, Marlieri Cichlid, Spotted Julie, Plaid Julie |
| Binominal name | Julidochromis marlieri |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | Up to 5 inches |
| Water parameters | Temp 73o to 81o F (23.0-27.0°C) pH 7.5-9.5 Hardness 10-25 |
| Tank level | Bottom – Middle |
| Diet | Omnivore |
| Lifespan | 5 to 8 years |
| Tank mates | Other Tanganyika cichlids that are similar size |
Honey Gourami (Trichogaster chuna)
| Common name(s) | Honey Gourami, Sunset Gourami, Red Flame Gourami |
| Binominal name | Trichogaster chuna |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 3.2 inches |
| Water parameters | Temp 72o to 82oF (22.2-27.8°C) pH 6.0 – 7.5 Harndess 4-10 dGH |
| Tank level | Middle – Top |
| Diet | Omnivore |
| Lifespan | 4 to 8 years |
| Tank mates | Small peaceful fish such as rasboras, tetras, and dwarf corydoras. Avoid aggressive or fin-nipping fish. |
Red Dwarf Gourami (Trichogaster lalius)
| Common name(s) | Red Dwarf Gourami, Flame Gourami, Powder Blue Gourami, Red Gourami, Sanset Gourami |
| Binominal name | Trichogaster lalius |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | Up to 4.5 inches |
| Water parameters | Temp 77o to 79o F (22.2-27.8°C) pH 6.0 – 8.0 Hardness 10-20 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 5 to 7 years |
| Tank mates | Plecos, sparkling and pearl gouramis, mollies, swordtails, platies, rasboras, loaches, tetras, catfish, mystery snails, and Amano shrimp. Avoid very active and fast fish that will compete for food |
Sparkling Gourami (Trichogaster pumila)
| Common name(s) | Sparkling Gourami, Pygmy Gourami |
| Binominal name | Trichogaster pumila |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.5 inches |
| Water parameters | 70o to 82o F (22.0-28.0°C) pH 5.0-7.5 Hardness 1-10 dGH |
| Tank level | Middle-Top |
| Diet | Omnivore |
| Lifespan | 5 years |
| Tank mates | Dwarf and Pearl Gouramis, Rasboras, Neon Rainbowfish, Corydoras, Tetras, or Otos. Fish such as male Bettas, Black Tetras, and Tiger Barbs should be avoided. |
Panda Corydoras Catfish (Corydoras panda)
| Common name(s) | Panda Corydoras Catfish, Panda Catfish, Panda Cory Cat |
| Binominal name | Corydoras panda |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 68o to 77oF (20-25°C) pH 6.0-8.0 Hardness 2-20 dGH |
| Tank level | Bottom |
| Diet | Omnivore |
| Lifespan | 10 years |
| Tank mates | Other Cories, Danios, Gouramis, Loaches, Rasboras, Tetras |
Albino Corydoras Catfish (Corydoras paleatus)
| Common name(s) | Albino Corydoras Catfish |
| Binominal name | Corydoras paleatus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 77o to 82o F (25.0-28.0°C) pH 6.0-8.0 Hardness 5-19 |
| Tank level | Bottom |
| Diet | Omnivore |
| Lifespan | 10 years |
| Tank mates | Mollies, Fancy Guppies, Neon Tetras, Angelfish, Danios, Platies, Swordtails, Gouramis, Shrimps |
Skunk Corydoras Catfish (Corydoras arcuatus)
| Common name(s) | Skunk Corydoras Catfish |
| Binominal name | Corydoras arcuatus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 68o to 77o F (20.0-25.0°C) pH 6.2-7.2 Hardness 2-12 dGH |
| Tank level | Bottom |
| Diet | Omnivore |
| Lifespan | 10 years |
| Tank mates | Plecostomus, Zebra Danio, White Cloud Mountain Minnow, and small schooling fish |
Red Fire Shrimp (Lysmata debelius)
| Common name(s) | Red Fire Shrimp, Cherry Red Shrimp, Blood Red Shrimp, or Scarlet Cleaner Shrimp |
| Binominal name | Lysmata debelius |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.5-2 inches |
| Water parameters | Temp 70o to 78o F pH 7.0-7.5 Hardness 4-8 dGH |
| Tank level | Bottom |
| Diet | Omnivore, algae eater |
| Lifespan | Up 2 years |
| Tank mates | Small, non-aggressive fish; recommended to keep shrimps and fish in separate tanks |
Tiger Shrimp (Caridina serrata)
| Common name(s) | Tiger Shrimp |
| Binominal name | Caridina serrata |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.25 inches |
| Water parameters | Temp 68o to 74o F (20.0-23.3°C) pH 6.0-7.5 Hardness 3-6 dGH |
| Tank level | Bottom-Middle |
| Diet | Omnivore, algae eater |
| Lifespan | 1 to 2 years |
| Tank mates | Other shrimp in the Caridina family, most common snails |
Amano Shrimp (Caridina multidentata)
| Common name(s) | Amano Shrimp, Algae Eating Shrimp, Yamato Shrimp, Japonica, Japanese Shrimp |
| Binominal name | Caridina multidentata |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 2 inches |
| Water parameters | Temp 70o to 80o F (21.1-27.6°C) pH 6.5-8.0 Hardness 5-15 dGH |
| Tank level | Bottom-Middle |
| Diet | Omnivore, algae eater |
| Lifespan | 2 to 5 years |
| Tank mates | Betta Fish, Guppies, Small Tetras, Peaceful Barbs like Cherry Barb, Other Small Fish like Zebra Danio |
Betta Fish (Betta splendens)
| Common name(s) | Betta fish, Siamese fighting fish |
| Binominal name | Betta splendens |
| Care Level | Easy |
| Temperament | Aggressive towards its own species and other brightly colored fish, peaceful towards non-aggressive tank mates |
| Size range –lenght | Up to 3 inches |
| Water parameters | Temp 75-82 F (24-28°C), pH 6.5-7.5, Hardness 5-20 dGH |
| Tank level | In the middle and top parts of the tank |
| Diet | Carnivore |
| Lifespan | 3-5 years |
| Tank mates | Snails, shrimp, bottom-dwelling fish such as Corydoras and Otocinclus catfish, peaceful mid and top level fish such as neon tetras and guppies. Avoid brightly colored and fin-nipping fish. It’s best to keep male Bettas alone or with a few carefully selected tank mates. Female Bettas can be kept in small groups. |
Scarlet Badis (Dario dario)
| Common name(s) | Scarlet Badis, Scarled Gem, Gem Badis |
| Binominal name | Dario dario |
| Care Level | Easy |
| Temperament | Semi-aggressive, species-only tank recommended |
| Size range –lenght | 0.8 inch |
| Water parameters | Temp 64,5o to 79o F (18.1-26.1°C) pH 6.5-8.5 Hardness 10-20 dGH |
| Tank level | Bottom-Middle |
| Diet | Primarily carnivorous |
| Lifespan | 3 to 6 years |
| Tank mates | A species-only tank is the ideal setup, but Celestial Pearl Danios, shrimp, and snails are some compatible tank mates. |
Dwarf Puffer (Carinotetraodon travancoricus)
| Common name(s) | Dwarf Puffer |
| Binominal name | Carinotetraodon travancoricus |
| Care Level | Intermediate |
| Temperament | Aggressive |
| Size range –lenght | 1.4 inches |
| Water parameters | Temp 72o to 82o F (22.2-27.8 °C) pH 6.5-7.5 Hardness 5-25 dGH |
| Tank level | Middle |
| Diet | Primarily carnivorous, prefers live foods |
| Lifespan | 4 years |
| Tank mates | Small Tetras, Corydoras Catfish, Otocinclus Catfish, Nerite Snails, Kuhli Loach |
Spotted Blue-eye (Pseudomugil gertrudae)
| Common name(s) | Spotted Blue-eye |
| Binominal name | Pseudomugil gertrudae |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1 inch |
| Water parameters | Temp 73o to 86o F (22-30°C) pH 4.5-7.5 Hardness 5-12 dGH |
| Tank level | Middle |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Small schooling fish, livebearers, small rainbowfish like M. praecox or Blue-Eyes, small catfish, Gudgeons, Garra |
Dwarf Sucker (Otocinclus macrospilus)
| Common name(s) | Otocinclus, otocinclus catfish, dwarf sucker, dwarf armored catfish, oto, oto cat, otto |
| Binominal name | Otocinclus macrospilus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 1.8 inches |
| Water parameters | Temp 73o to 86o F (21-26°C) pH 5.5-7.5 Hardness up tp 12 dGH |
| Tank level | All levels |
| Diet | Omnivore |
| Lifespan | 3 to 5 years |
| Tank mates | Other oto catfish, Cherry barbs, Angelfish, Danios, Corydoras, Tetras, Mollies, Guppies, Harlequin rasboras, Zebra loaches, Dwarf gouramis, Snails, Shrimp |
Goldfish (Carassius auratus)
| Common name(s) | Goldfish |
| Binominal name | Carassius auratus |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 6 inches but depends on species |
| Water parameters | Temp 65o to 72o F (18.3-22.2°C) pH 6.0-8.0 Hardness 5-19 dGH |
| Tank level | All Levels |
| Diet | Omnivore |
| Lifespan | 10 to 20 years |
| Tank mates | Rosy Barbs, Zebra Danios, Giant Danios, White Cloud Mountain Minnows, Dojo Loach, Banded Corydoras, Platym, Hillstream Loach, Hog-Nosed Brochis, Bristlenose Pleco, Rubbernose Pleco, Hoplo Catfish, Mystery Snail |
Bristlenose Catfish (Ancistrus)
| Common name(s) | Bristlenose Catfish |
| Binominal name | Ancistrus |
| Care Level | Easy |
| Temperament | Aggressive as adults |
| Size range –lenght | 3.5 inches |
| Water parameters | Temp 69o to 80oF (20.6-26.1°C) pH 5.5-7.5 Hardness 6-10 |
| Tank level | Bottom |
| Diet | Omnivore, algae-eaters |
| Lifespan | 12 years |
| Tank mates | Guppies, Tetras, Minnows, Mollies, Platies, Gouramis, Cory catfish, Cherry barbs, Tiger barbs, Zebra danios, Hatchetfish, Silver dollars, Clown loaches, Kuhli loaches, bamboo shrimp, mystery snails, and nerite snails. |
Common Molly (Poecilia sphenops)
| Common name(s) | Molly fish, molly, common molly, short-finned molly |
| Binominal name | Poecilia sphenops |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | 4.5 inches |
| Water parameters | 72o to 78o F (22.2-25.6°C) pH 6.5-8.5 Hardness 15-30 dGH |
| Tank level | All levels |
| Diet | Omnivore |
| Lifespan | 5 years |
| Tank mates | Guppies, Danios, Platys, Gouramis, Tetras, Angelfish, Swordtails, Some cichlids (dwarf cichlids, keyhole cichlids, ram cichlids) |
Mystery Snail (Pomacea bridgesii)
| Common name(s) | Mystery Snail, Golden Apple Snail, Florida Apple Snail, Titan Apple Snail |
| Binominal name | Pomacea bridgesii |
| Care Level | Easy |
| Temperament | Peaceful |
| Size range –lenght | Up to 2 inches |
| Water parameters | 65o to 82oF (18.3-27.8°C) pH 7.5-8.5 Hardness 7-18 dGH |
| Tank level | All levels |
| Diet | Omnivore |
| Lifespan | 2 years |
| Tank mates | Small shrimp, Bettas, Tetras, Gouramis, Danios, Mollies, Platies, Guppies, Nerite snails |
In conclusion
Determining the appropriate number of fish to keep in a 20-gallon tank requires careful consideration of several factors.
While it is possible to house a variety of fish in this tank size, it is crucial to prioritize the well-being and comfort of the fish. Overstocking can lead to water quality issues, stress, and health problems for the fish.
By adhering to responsible stocking practices, you can achieve a harmonious balance within your 20-gallon tank, providing a captivating and rewarding experience for both the fish and yourself.
