Can You Keep Angelfish In A 20-Gallon Tank? (Practical Tips)

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If you’ve recently acquired a 20-gallon tank and are curious about keeping angelfish in it, you’re in the right spot.

In this article, I’ll delve into the number of angelfish that can comfortably live in a tank of this size and offer some handy advice on raising them optimally in 20 gallons.

You’ll also discover which fish species can cohabitate with angelfish in such a setting and whether breeding is a viable option.

Let’s get started.

Can You Put Angelfish in 20 Gallons?

Yes, you can keep angelfish in a 20-gallon tank, but it’s not ideal for long-term care. A more spacious environment is recommended for their optimal well-being.

  • Juvenile Stage: While young angelfish can start in a 20-gallon tank, they will outgrow it. Angelfish can reach up to 6 inches in height as adults.
  • Territorial Nature: Angelfish can become territorial, especially in tight spaces. A cramped tank can increase stress and aggression.
  • Group Dynamics: Angelfish are often happier in groups. A 20-gallon tank limits the number of fish, potentially causing social stress.
  • Water Quality: Larger volumes of water maintain stable conditions easier. A smaller tank can have quicker toxin build-up, affecting angelfish health.

Also Read: Angelfish Tank Size

Why Is 20 Gallons Seen as the Minimum Size for Housing Angelfish?

Twenty gallons is often cited as the minimum size for housing angelfish because it provides a starting space for juveniles and maintains water quality more easily than smaller tanks. 

However, as the fish grow, a larger environment is imperative for their well-being.

  • Growth Potential: Juvenile angelfish are small, but they can grow up to 6 inches in height. A 20-gallon tank offers an initial suitable environment for their growth phase.
  • Water Stability: Smaller tanks can experience rapid changes in water conditions. A 20-gallon volume helps buffer against sudden temperature shifts and toxin build-ups.
  • Stress Reduction: While still not spacious, 20 gallons can provide a degree of comfort for young angelfish, reducing stress levels that can arise in tighter confines.

Also Read: Can Angelfish Live In A 10-Gallon Tank?

How Many Angelfish Can Be Kept Together In 20 Gallons?

In a 20-gallon tank, you can initially house two juvenile angelfish, but as they grow, the space becomes inadequate.

For adult angelfish, a 20-gallon tank is insufficient for even one individual.

  • Juveniles (0-6 months): Young angelfish, usually up to 2 inches in size, can be housed in pairs in a 20-gallon tank but will soon outgrow this space.
  • Sub-Adults (6-12 months): As they approach 4 inches, it’s pressing to provide a more spacious environment. One might manage, but two would be a crowd.
  • Adults (12+ months): Mature angelfish, reaching up to 6 inches or more, need more space. A single adult would be constrained in a 20-gallon setup.
  • Territorial Behavior: With limited space, angelfish can exhibit increased aggression, especially during their growth phase when they establish territories.

Also Read: How Many Angelfish In A 30-Gallon Tank?

Tips for Successfully Keeping Angelfish in a 20-Gallon Environment

Keeping angelfish in a 20-gallon tank is challenging but can be managed with proper care and attention.

For the best results, it’s crucial to adopt specific practices tailored to such a limited space.

  • Stock Judiciously: Start with 1-2 juvenile angelfish; as they grow past 2 inches, consider relocating to prevent crowding.
  • Water Quality: Perform weekly water changes, replacing 5 gallons (25%) with dechlorinated water to maintain clarity and balance.
  • Filter Appropriately: Invest in a filter rated for 30-40 gallons, ensuring efficient waste removal and promoting water circulation. My recommendation: Fluval C4 Power Filter (link to Amazon).
  • Provide Hiding Spots: Add dense plants like Java fern and decorations, allowing fish to establish territories and hide.
  • Monitor Behavior: Watch for signs of aggression or stress, like nipping, and adjust the environment or stock as needed.
  • Diet Consideration: Feed a varied diet; small pinches of flake food and bloodworms 1-2 times daily ensures proper nutrition.

Does the Gender of the Angelfish Matter?

Yes, the gender of the angelfish does matter, especially in a confined space like a 20-gallon tank. The gender can influence behavior, compatibility, and breeding dynamics.

  • Territorial Behavior: Male angelfish can be more territorial than females. Two males in a 20-gallon tank might show increased aggression.
  • Breeding Pairs: If you have a male and female, they might form a pair and breed. This can lead to additional space needs and aggression towards other fish.
  • Space Allocation: A breeding pair will claim a large portion of the tank, making it challenging for other fish to coexist peacefully.
  • Observing Interactions: Males may chase or nip at females if not interested in breeding. Monitoring behavior is essential to prevent undue stress.

What Happens If You Cram Too Many Angelfish into the Tank?

Overstocking a tank with angelfish leads to increased stress, health problems, and territorial disputes.

The environment becomes suboptimal, and fish will suffer both behaviorally and physically.

  • Stress Levels Rise: Overcrowding can result in constant chasing and reduced hiding spots, leading to chronic stress for the fish.
  • Water Quality Degrades: More fish means more waste, which can spike ammonia and nitrite levels, endangering fish health.
  • Disease Spreads Faster: Tight spaces can facilitate rapid transmission of illnesses like fin rot or ich among the fish population.
  • Limited Growth: Angelfish in overcrowded conditions might experience stunted growth due to stress and competition for resources.
  • Aggression Increases: With limited territories, fights can become more frequent, resulting in injuries or even fatalities.

Is Breeding Angelfish Possible in a 20-Gallon Setting?

Yes, breeding angelfish in a 20-gallon tank is possible, but it presents challenges due to the limited space. A dedicated breeding setup and careful management are crucial for success.

  • Dedicate the Tank: Ideally, use the 20-gallon tank solely for the breeding pair. This reduces competition and territorial disputes.
  • Optimize Water Conditions: Maintain a pH of 6.5-7.2 and a temperature of 80°F (27°C) to promote breeding behaviors.
  • Introduce Breeding Surfaces: Add broad-leaved plants or a vertical flat slate. Angelfish prefer laying their eggs on vertical surfaces.
  • Monitor Diet: Feed a high-quality, varied diet. Include live foods, such as brine shrimp, to condition the pair for breeding.
  • Increase Water Changes: Boost water changes to 40-50% weekly. Clean water stimulates spawning behaviors.
  • Isolate Fry: Once eggs hatch, consider moving fry to a separate tank with a sponge filter, ensuring their safety and providing space for growth.
  • Fry Diet: Initially feed fry liquid fry food or newly hatched brine shrimp. As they grow, transition to finely crushed flake food.
  • Regular Observations: Keep a close eye on the breeding pair. If they repeatedly eat their eggs, consider artificially hatching eggs in a separate container with gentle aeration.

How Many Angelfish Should Be Kept Together in General?

In general, angelfish thrive best in groups of five or more to diffuse aggression and exhibit natural schooling behavior.

However, the tank size and environment play pivotal roles in determining the optimal number.

  • Natural Behavior: In the wild, angelfish are semi-aggressive cichlids that move in shoals. A group helps distribute aggression, preventing bullying of a single fish.
  • Tank Size Matters: For a group of five angelfish, a minimum of 55 gallons is recommended. This provides adequate space for growth, movement, and territorial establishment.
  • Mating Concerns: In larger groups, there’s a higher chance of forming pairs. Observing interactions and potentially separating pairs can prevent breeding-related aggression.

Pairing Angelfish with Other Species in a 20-Gallon Tank

Pairing angelfish with other species in a 20-gallon tank requires careful consideration due to space constraints and compatibility concerns.

It’s crucial to select peaceful, smaller species that won’t become a target for the angelfish and won’t outcompete them.

Here’s a simple table summarizing what I am about to discuss:

Fish CombinationNumber of Fish (20-Gallon Tank)
Angelfish + Corydoras Catfish1 Angelfish, 3-4 Corydoras
Angelfish + Neon Tetras1 Angelfish, 6 Neon Tetras
Angelfish + Dwarf Gouramis1 Angelfish, 1-2 Dwarf Gouramis
Angelfish + Harlequin Rasboras1 Angelfish, 5 Harlequin Rasboras
Angelfish + Bristlenose Pleco1 Angelfish, 1 Bristlenose Pleco
Angelfish + Cherry Shrimp1 Angelfish, Small colony of Cherry Shrimp
Angelfish + Mollies1 Angelfish, 2-3 Mollies
  • Corydoras Catfish: 3-4 of these peaceful bottom dwellers can coexist well. Their active scavenging helps maintain substrate cleanliness.
  • Neon Tetras: A small school of 6 can be added, but monitor closely as larger angelfish might see them as food.
  • Dwarf Gouramis: 1-2 of these calm fish can add color. Ensure plenty of plants for them to hide and explore.
  • Harlequin Rasboras: A group of 5 provides a beautiful contrast. They’re peaceful and usually stay in the mid-water region.
  • Bristlenose Pleco: Just one can be added. It’ll help control algae but ensure it has hiding spots.
  • Cherry Shrimp: A small colony can coexist, but provide dense plants for hiding. Be cautious as larger angelfish might hunt them.
  • Mollies: 2-3 can be accommodated. They prefer harder water, so monitor water parameters to ensure both species’ needs are met.
Pleco with angelfish

Species to Steer Clear of in a 20-Gallon Setup with Angelfish

When housing angelfish in a 20-gallon tank, it’s vital to avoid certain species that might pose compatibility or space challenges.

Many commonly considered tankmates aren’t suitable for such a confined setup with angelfish.

  • Other Cichlids: Many cichlids are territorial and can clash with angelfish. For example, Ram cichlids need their own territory, leading to disputes.
  • Barbs: Species like Tiger Barbs can be fin-nippers and may harass the angelfish, causing them stress and potential injury.
  • Larger Catfish: Common plecos, for instance, grow too large and can outcompete angelfish for space and food.
  • Discus: While they are peaceful, their size and specific care requirements make a 20-gallon tank too restrictive for both species.
  • Guppies: Their bright colors and flowing fins might attract unwanted attention, with angelfish potentially seeing them as prey.
  • Goldfish: They require colder water temperatures and different diets, making them incompatible with tropical angelfish.
  • Bettas: Known for their aggression, especially male bettas, they can engage in territorial disputes with angelfish, stressing both species.
Tiger Barb


For quick readers, here’s a short summary:

  • A 20-gallon tank can house juvenile angelfish, but adults require more space due to their size and territorial nature.
  • Although 20 gallons is the minimum recommended size for angelfish, it is merely a starting point for juveniles, and a larger tank becomes necessary as they grow.
  • Initially, two juvenile angelfish can be kept in a 20-gallon tank, but space becomes inadequate as they mature.
  • Breeding angelfish in a 20-gallon tank is possible with proper setup and care, but the limited space poses challenges.
  • Pairing angelfish with other species in a 20-gallon tank requires careful species selection, with some species being incompatible due to size or behavior.