Best Fish For A 36-Gallon Tank: A Comprehensive Guide

Fishkeeping is a fun and interesting hobby, but Selecting the appropriate fish for your tank cannot be easy. A 36-gallon tank is popular for those looking to set up a medium-sized aquarium. 

However, selecting the perfect fish for your tank can take time and effort with so many different types of fish available. 

This comprehensive guide explores the best fish for a 36-gallon tank, along with their characteristics, behaviour, and compatibility with other fish.

Considerations For Choosing Best Fish For A 36-Gallon Tank

Selecting fish for a 36-gallon aquarium requires careful consideration of various factors to ensure a healthy and thriving aquatic environment. Here are the key factors to consider:

  1. Tank Size: 

The size of the tank is crucial as it determines the space available for the fish to swim and thrive. Different fish species have varying space requirements, so choosing an appropriately sized tank that accommodates their needs is essential.

  1. Water parameters

Maintaining suitable water parameters is vital for the well-being of the fish. Factors such as temperature, pH level, hardness, and ammonia levels should be monitored and adjusted within the appropriate range for the chosen fish species.

  1. Fish Compatibility: 

Some fish species may exhibit aggressive behaviours or have specific social needs. Researching the compatibility and temperament of different fish species is important to ensure they can coexist peacefully in the aquarium. Compatibility also extends to factors such as preferred water conditions and swimming patterns.

  1. Feeding Habits: 

Understanding the dietary needs of the fish is crucial for providing a balanced and appropriate diet. Different fish species may have specific feeding habits, such as being herbivores, carnivores, or omnivores. Offering a varied diet that meets their nutritional requirements contributes to their overall health and vitality.

  1. Behavioural Characteristics: 

Each fish species has its own behavioural traits and preferences. Some fish are active swimmers, while others prefer hiding or staying near the bottom of the tank. Providing suitable tank decorations, hiding places, and open spaces can help accommodate their natural behaviours and reduce stress.

  1. Type Of Filtration: 

The right filtration system is essential for maintaining water quality. Mechanical, chemical, and biological filters serve different purposes in removing debris, toxins, and excess nutrients from the aquarium.

Choosing an appropriate filtration system based on the tank size and requirements is crucial for the fish’s well-being and overall water quality.

By considering these factors, including tank size, water parameters, fish compatibility, feeding habits, behavioural characteristics, and type of filtration, you can create an ideal environment for your aquarium inhabitants. 

Providing the right conditions promotes your fish’s health, happiness, and longevity.

CIf you’re looking for the best fish to keep in a 36-gallon aquarium, here are the top 5 options:

  1. Neon Tetra: 

Neon Tetras are small, peaceful fish known for their vibrant blue and red stripes. They are active swimmers and do well in schools. Neon Tetras prefer slightly acidic water with a temperature range of 72-78°F. They are compatible with other small, peaceful fish and have an omnivorous diet.

  1. Molly: 

Mollies are small, lively fish available in various colors. They thrive in social groups and prefer slightly alkaline water with a temperature range of 75-82°F. Mollies are compatible with other small, peaceful fish and have an omnivorous diet that includes algae, flakes, and live foods.

  1. Dwarf Gourami: 

Dwarf Gouramis are colorful fish with a peaceful temperament. They are active and social, making them great additions to a community tank. Dwarf Gouramis prefer slightly acidic water with a temperature range of 72-78°F. They should be kept with peaceful tank mates that do not nip fins. Their diet consists of flakes, freeze-dried, and live foods.

  1. Harlequin Rasbora: 

Harlequin Rasboras are small and colorful fish with black triangular markings on their bodies. They are active and peaceful, making them suitable for community aquariums. Harlequin Rasboras prefer slightly acidic water with a temperature range of 72-78°F. They are compatible with other small, peaceful fish and have an omnivorous diet.

  1. Honey Gourami: 

Honey Gouramis are peaceful and colorful fish with a unique body pattern. They are active and social, and they prefer slightly acidic water with a temperature range of 72-82°F.

Honey Gouramis should be kept with non-aggressive tank mates. Their diet mainly consists of flakes and live foods.

When choosing fish for a 36-gallon aquarium, it’s essential to consider their compatibility with each other, water parameters, and feeding habits. These five species are well-suited to a 36-gallon tank and can provide an engaging and visually appealing display.

Other Compatible Fish For A 36 Gallon Tank

Apart from the top five best fish for a 36-gallon aquarium, here are some other compatible fish options:

  1. Zebra Danio: 

Active and schooling fish that thrive in groups. They are hardy and compatible with a variety of community fish. Water parameters should be kept at a pH of 6.5-7.0 and a temperature of 64-75°F.

  1. Cherry Barb: 

Peaceful and colorful fish that do well in small groups. They prefer slightly acidic water with a pH of 6.0-7.0 and a temperature of 72-79°F.

  1. Pearl Gourami: 

Beautiful and peaceful fish known for their iridescent scales. They prefer slightly acidic to neutral water with a pH of 6.5-7.5 and a temperature of 72-82°F.

  1. Platy: 

Hardy and peaceful fish available in various colors. They thrive in groups and prefer a pH of 7.0-8.0 and a temperature of 70-82°F.

  1. Corydoras Catfish:

Small, bottom-dwelling fish that are social and peaceful. They help keep the tank clean by scavenging for food. They prefer a pH of 6.0-7.5 and a temperature of 72-78°F.

  1. Betta Fish: 

While Betta fish are typically kept solitary, a 36-gallon tank can provide enough space for a single Betta fish along with appropriate tank mates. Ensure that tank mates are peaceful and won’t nip the Betta’s fins.

These fish can coexist peacefully in a 36-gallon tank when their specific requirements for water parameters, tank size, and compatibility are met. Always research the needs of each fish species and monitor their behavior to ensure a harmonious and thriving aquarium.

Incompatible Fish For A 36 Gallon Tank

Fish that are not compatible with a 36-gallon aquarium include:

  • Cichlids
  • Oscar Fish
  • Guppies (in some cases)
  • Large Angelfish
  • Goldfish

Tank Setup And Maintenance

Maintaining a clean and healthy environment in a 36-gallon aquarium requires regular tank setup and maintenance. Here are the steps to follow:

  • 1. Perform a 25% water change every week: Regular water changes help remove accumulated waste, toxins, and excess nutrients from the aquarium. Aim to replace approximately 25% of the water in the tank with fresh, dechlorinated water each week. This helps maintain water quality and prevents the buildup of harmful substances.
  • 2. Clean the aquarium filter and replace its filter cartridges every month: The aquarium filter plays a crucial role in removing debris and maintaining water clarity. Regularly clean the filter by rinsing the filter media and replacing the filter cartridges as per the manufacturer’s instructions. This ensures efficient filtration and prevents clogging.
  • 3. Keep the pH level and temperature stable: Many fish species are sensitive to fluctuations in pH and temperature. Monitor the water parameters regularly using a reliable test kit and adjust them if necessary. Maintain a stable pH level within the appropriate range for the fish species in the aquarium. Additionally, ensure that the water temperature remains consistent and matches the requirements of the fish.
  • 4. Only feed the fish the amount they can consume in three to five minutes: Overfeeding can lead to excessive waste and poor water quality. Feed your fish a small amount of food that they can consume within three to five minutes. This prevents overfeeding and helps maintain the water quality in the aquarium. Remove any uneaten food promptly to prevent it from decomposing and affecting the water parameters.
  • By following these tank setup and maintenance practices, you can ensure a clean and healthy environment for your 36-gallon aquarium. Consistent care and attention will promote the well-being of your fish and create an enjoyable aquatic habitat.

Frequently Asked Questions

Q. How many fish can I keep in a 36-gallon tank?

A. The number of fish you can keep in a 36-gallon tank depends on several factors, including the size and species of the fish, their activity level, and their compatibility. As a general guideline, you can keep approximately 1 inch of fish per gallon of water. This means that in a 36-gallon tank, you can have around 36 inches of fish, considering their adult size.

However, it’s essential to research the specific needs and requirements of each fish species to ensure they have enough space and a suitable environment to thrive.

Q. Can I keep a Betta fish in a 36-gallon tank?

A. Yes, you can keep a Betta fish in a 36-gallon tank. However, it’s important to note that Betta fish are solitary and territorial by nature. They prefer to have their own space and can become stressed or aggressive if housed with other fish, especially males.

In a 36-gallon tank, you can provide ample swimming space and plenty of hiding spots and enrichment for your Betta fish. Just ensure that the tank is properly decorated and that the water parameters, such as temperature and pH, are maintained within the appropriate range for Betta fish.

Q. Can I keep Goldfish in a 36-gallon tank?

A. No, it is not recommended to keep Goldfish in a 36-gallon tank. Goldfish require larger tank sizes due to their size and produce more waste, which can lead to poor water quality in a smaller tank.


Choosing the best fish for a 36-gallon tank can be challenging, but it can be a fun and rewarding experience with the right knowledge and information. 

From the serene neon tetra to the flamboyant honey gourami, a variety of fish can thrive in a 36-gallon aquarium. 

The key is ensuring that the fish are compatible with each other and that the water quality is kept at optimal levels through regular maintenance and care. 

With the knowledge from this guide, you can now confidently select the perfect fish for your 36-gallon tank that will add colour, beauty, and serenity to your home.

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