How Many Angelfish In A 40-Gallon Tank? (With Examples)

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Angelfish are a perfect pick if you’re scouting for new fish for your 40-gallon tank. They’re both stunning and tranquil, making them a joy to have.

But, how many angelfish can comfortably fit in a 40-gallon space? What’s the limit? If they reproduce, are there challenges? And what about other fish varieties to accompany them?

In this article, I’ll cover these questions and several others, so you leave with all the information you need. Let’s jump right in.

How Many Angelfish Fit in a 40-Gallon Tank?

In a 40-gallon tank, you can comfortably keep 2 to 3 adult angelfish. Too many angelfish in such a space can lead to stress and territorial disputes.

  • Space Requirement: Each angelfish needs 10-20 gallons. For example, with 20 gallons per fish, a 40-gallon tank can hold 2 adults comfortably.
  • Territorial Nature: Angelfish mark areas up to 12 inches. Too many and they’ll clash over space, leading to visible fin nips and stress.
  • Water Quality: With 2 fish, change 10% water weekly. Overstocking means more waste, leading to frequent and larger water changes.
  • Breeding Considerations: A breeding pair needs about half the tank. If they lay eggs, they’ll defend a 20-gallon space aggressively.

Here’s how I usually do these calculations:

  • Angelfish can grow to be 6 inches tall when fully mature.
  • Using the 1-inch-per-gallon rule: 6 inches of fish would need 6 gallons of water.
  • A 40-gallon tank divided by the 6 gallons needed for each angelfish gives approximately 6.67.
  • Rounded down, this suggests that about 6 juvenile angelfish could technically fit in a 40-gallon tank.
  • However, this doesn’t account for their territorial nature and other factors, hence the practical recommendation of 2 to 3 adults.

Also Read: Angelfish Tank Size

Why Is a 40-Gallon Tank Popular for Angelfish?

A 40-gallon tank is often chosen for angelfish because it offers ample space for their growth and well-being.

This size strikes a balance between the fish’s needs and practicality for home aquarists.

  • Growth Space: Adult angelfish can reach 6 inches in height. A 40-gallon tank provides room for 2 to 3 to swim and grow comfortably.
  • Water Stability: Larger tanks like 40-gallons maintain stable water parameters better. For instance, slight temperature fluctuations are less impactful compared to smaller tanks.
  • Decor and Plants: Angelfish enjoy planted environments. A 40-gallon tank offers enough space for plants like Amazon Swords without crowding the fish.
  • Breeding Opportunity: For enthusiasts considering breeding, a 40-gallon allows a pair to stake territory and raise fry without overly stressing other tank mates.

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

How Do You Care for Angelfish in a 40-Gallon Tank?

Caring for angelfish in a 40-gallon tank involves ensuring the right water conditions, nutrition, and environment for their well-being.

Proper attention to their needs will result in healthy, vibrant fish.

  • Water Quality: Maintain a pH of 6.5 to 7.5. Use a reliable water conditioner to neutralize harmful substances during water changes. I use the Tetra AquaSafe (link to Amazon) precisely for this purpose.
  • Temperature Control: Angelfish thrive at 76-82°F. Invest in a quality heater and thermometer to maintain this range.
  • Regular Feeding: Offer a varied diet; flakes, live foods like brine shrimp, and frozen treats. Feed them once or twice daily.
  • Tank Setup: Use tall plants and driftwood. This mimics their natural habitat and offers hiding spots.
  • Filtration: A quality filter rated for 40-gallons or more is crucial. This ensures clean water and adequate oxygenation. My go-to choice is the Fluval C4 Power Filter (link to Amazon).
  • Tank Mates: Opt for non-aggressive companions like tetras or corydoras. Avoid fin-nipping species to prevent stress.
  • Health Checks: Regularly observe for signs of disease: clamped fins, spots, or abnormal behavior. Early detection is key for effective treatment.

What Happens If I Put Too Many Angelfish in a 40-Gallon Tank?

Overstocking a 40-gallon tank with angelfish can lead to stress, territorial disputes, and potential health issues.

The environment becomes less optimal, and the quality of life for each fish decreases.

  • Increased Aggression: Angelfish are territorial; with limited space, they may fight for dominance, leading to injuries like torn fins.
  • Water Quality Deterioration: More fish produce more waste. High ammonia and nitrite levels can arise, posing health risks to all inhabitants.
  • Stress and Disease: Crowded conditions increase stress, making fish susceptible to illnesses like ich or fin rot, which can spread rapidly.
  • Limited Growth and Development: In cramped spaces, fish can’t grow to their full potential. They may become stunted or exhibit deformities over time.

Also Read: How Many Angelfish In A 55-Gallon Tank?

Do Male and Female Angelfish Need Different Care?

Male and female angelfish generally have similar care requirements, but their interactions differ based on gender in a tank environment.

For a 40-gallon tank, maintaining a harmonious male-to-female ratio can ensure a peaceful environment and minimize aggressive encounters.

  • Mating Pairs: In a 40-gallon tank, 1 male and 1 female can form a bonded pair for breeding. They’ll establish and guard their territory.
  • Gender Ratios: To minimize aggression, have more females than males. A ratio of 1 male to 2 or 3 females can reduce potential male confrontations.
  • Territorial Behavior: Males tend to be more territorial. Multiple males in a 40-gallon might lead to persistent territorial battles.
  • Spawning Territories: If a pair decides to spawn, they’ll defend their space aggressively. Given the tank size, one breeding pair is optimal to prevent spawning-related conflicts.

Can You Breed Angelfish in a 40-Gallon Tank?

Yes, a 40-gallon tank is an appropriate size for breeding angelfish. With the right conditions and care, your angelfish pair can successfully spawn and raise their fry.

  • Establishing Territory: Provide natural barriers using plants and decorations. This helps the breeding pair establish a secure spawning site.
  • Optimal Conditions: Maintain water pH between 6.5-7.5 and a temperature of 80°F. This encourages spawning behavior.
  • Dietary Needs: Feed a varied diet including live foods. High-quality nutrition ensures healthy eggs and boosts breeding likelihood.
  • Protection for Fry: Once eggs are laid, consider a divider or separate tank. This protects fry from other potential tank mates.

What’s the Best Number of Angelfish to Keep Together?

When it comes to angelfish, they often fare best when kept in pairs or small groups, allowing for social interaction without excessive territorial disputes.

The ideal number largely depends on the tank size and the specific goals of the aquarist.

  • Natural Behavior: In the wild, angelfish are semi-aggressive and territorial. Keeping them in pairs or small groups of 5-6 allows for social dynamics without overburdening space.
  • Tank Size Matters: Generally, a 55-gallon or larger tank can accommodate a group of 5-6 angelfish comfortably. Smaller tanks should house fewer fish.
  • Breeding Considerations: If breeding is a goal, pairs work best. In group settings, multiple pairs might result in territorial conflicts, especially during spawning.

Which Fish Get Along with Angelfish in a 40-Gallon Tank?

Angelfish, being semi-aggressive, are selective about their tank mates, especially in a 40-gallon tank.

Choosing the right companions ensures harmony, reduces stress, and maintains a vibrant aquarium community.

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

Fish CombinationNumbers in a 40-Gallon Tank
Angelfish + Corydoras2-3 Angelfish, 5-6 Corydoras Catfish
Angelfish + Tetras2-3 Angelfish, 10-12 Tetras (e.g., Rummy-nose)
Angelfish + Dwarf Gouramis2-3 Angelfish, 2-3 Dwarf Gouramis
Angelfish + Bristlenose Pleco2-3 Angelfish, 1 Bristlenose Pleco
Angelfish + Rasboras2-3 Angelfish, 8-10 Rasboras (e.g., Harlequin)
Angelfish + Mollies2-3 Angelfish, 4-5 Mollies
Angelfish + Kuhli Loaches2-3 Angelfish, 4-6 Kuhli Loaches
  • Corydoras Catfish: These peaceful bottom-dwellers can be kept in groups of 5-6. They’ll scavenge for leftover food and won’t bother the angelfish.
  • Tetras: Species like Rummy-nose or Black Skirt Tetras are good choices. A school of 10-12 tetras can coexist with angelfish without issue.
  • Dwarf Gouramis: Their calm demeanor complements angelfish. 2-3 gouramis can fit comfortably with angelfish in the tank.
  • Bristlenose Plecos: A beneficial algae eater, one Bristlenose Pleco won’t intrude on angelfish territories.
  • Rasboras: Harlequin or Scissortail Rasboras can be added. A group of 8-10 rasboras maintains balance with the angelfish.
  • Mollies: These adaptable fish are good neighbors. Keep a group of 4-5 mollies to ensure harmony with angelfish.
  • Kuhli Loaches: These nocturnal bottom-dwellers stay out of the angelfish’s way. A group of 4-6 loaches works well in a 40-gallon setup with angelfish.
Bristlenose Pleco

Which Fish Shouldn’t Be in a 40-Gallon Tank with Angelfish?

While angelfish are a popular choice for many aquarists, certain fish species aren’t ideal to be housed with them in a 40-gallon tank due to aggression, territorial disputes, or dietary differences.

It’s vital to choose tank mates that won’t stress or harm the angelfish.

  • Large Cichlids: Fish like Oscars or Jack Dempseys can be too aggressive. They may bully or even eat smaller angelfish.
  • Fin-Nippers: Fish such as Tiger Barbs or Serpae Tetras tend to nip fins. Angelfish, with their long, flowing fins, can be prime targets.
  • Small Fry-like Fish: Tiny fish, like Neon Tetras, may be mistaken for food. They can become an easy meal for adult angelfish.
  • Aggressive Bottom Dwellers: Red-tailed Black Sharks or larger plecos might claim the bottom area and chase away angelfish.
  • Territorial Mates: Betta fish, especially males, can be territorial and might confront similarly shaped angelfish.
  • Fish Needing Cooler Water: Species like Goldfish prefer colder waters. This contrasts with the tropical requirements of angelfish.
  • Very Active Swimmers: Fish like Danios can stress angelfish with their constant activity and quick movements in a confined 40-gallon space.
Jack Dempsey


For quick readers, here’s a short summary:

  • A 40-gallon tank can comfortably house 2 to 3 adult angelfish; overstocking may lead to stress and territorial disputes.
  • Angelfish are semi-aggressive and territorial, and while they can be kept in pairs or small groups, the tank size and breeding goals affect the ideal number.
  • Angelfish have specific care requirements in a 40-gallon tank, such as water quality, temperature control, and dietary needs, to ensure their well-being.
  • Suitable tank mates for angelfish in a 40-gallon setup include Corydoras Catfish, Tetras, and Dwarf Gouramis, while fish like large Cichlids, fin-nippers, and very active swimmers should be avoided.
  • A 40-gallon tank is popular for angelfish because it offers a balance between ample space for growth and practicality for home aquarists, allowing for breeding opportunities and decorated environments.