How Many Fish in a 5-Gallon Tank?

Are you considering setting up a beautiful 5-gallon fish tank in your home or office? Knowing the optimal number of fish and compatible species to include is crucial for maintaining a healthy aquatic environment.

how many fish 5 gallon tank

This article will guide you through the steps on determining how many fish can safely dwell in your 5-gallon tank, as well as provide you with some useful tips and recommendations on fish species and tank maintenance.

What are the Dimensions of a 5-Gallon Tank?

When planning your aquarium setup, it is essential to know the dimensions of the tank. A standard 5-gallon tank typically measures 16 inches long, 8 inches wide, and 10 inches high. However, there are different shapes and styles available, such as rectangular, hexagonal, and bow-front tanks. These alternative designs may have slightly different dimensions.

  • Rectangular tank: The most common shape, providing a large surface area for gas exchange and easy maintenance. They typically measure 16″ L x 8″ W x 10″ H.
  • Hexagonal tank: These tanks offer a unique aesthetic but may limit available swimming space for fish. Dimensions vary based on the manufacturer, but a 5-gallon hexagonal tank might measure approximately 12″ W x 14″ H.
  • Bow-front tank: This stylish tank provides an illusion of depth, with the curved front glass bowing outwards. A 5-gallon bow-front tank typically measures around 16″ L x 7.5″ W x 13″ H.

Keep in mind that the dimensions of the tank will impact the type and number of fish you can host, as well as the equipment and decorations you choose. In general, a longer, wider tank allows for better swimming space, while a taller tank provides more vertical space for decorations, plants, and hiding spots.

A standard 5-gallon tank measures 16″ L x 8″ W x 10″ H, but alternative shapes and styles may have slightly different dimensions. Consider the available space, equipment, and fish species when selecting a 5-gallon aquarium.

How Does Tank Size Affect Fish?

Tank size plays a crucial role in the overall health and well-being of your fish. In short, a larger tank provides better water quality, stable parameters, and more space for your fish to swim and explore. Let’s delve deeper into the impact of tank size on fish.

  • Water quality: Smaller tanks like a 5-gallon tank have less water volume, which means that waste and toxins can accumulate more quickly. This creates a more unstable environment for your fish, and a greater need for frequent water changes to maintain clean and healthy water conditions.
  • Stable Parameters: Temperature, pH, and other chemical parameters can fluctuate more easily in small tanks. These changes can stress your fish, leading to health issues. A larger tank provides more stable conditions, allowing your fish to thrive.
  • Aquatic community: Tank size also affects the number and types of fish you can safely house together. With a 5-gallon tank, you’re limited to only a few small fish or one larger fish. Overcrowding can lead to aggression and territorial behavior, as well as unhealthy water conditions.
  • Swimming space: Fish are naturally active animals that need space to move around. A small tank can restrict their movement and make them more prone to stress and disease. Providing an appropriately sized tank ensures your fish have ample room to swim and exhibit natural behaviors.

Tank size has a direct impact on the health, happiness, and longevity of your fish. It’s essential to carefully consider the appropriate tank size for your aquatic pets to create a comfortable and suitable environment.

Why is Important to Have a Good Filter in Your 5-Gallon Tank?

A good filter is crucial in a 5-gallon tank to ensure an optimal environment for your fish. The reasons why a good filter is important include maintaining water quality, removing waste products, providing oxygen, and promoting the growth of beneficial bacteria.

  • Water Quality: The filter cleans the water by trapping particles and debris, ensuring that the water stays clear and healthy. Without a good filter, the water quality in your tank can rapidly decrease, causing stress and potential harm to your fish.
  • Waste Removal: Fish produce waste, which can accumulate in the tank and create an unhealthy environment. A good filter effectively removes waste by breaking it down into smaller particles that can be safely handled by the bacterial cycle.
  • Oxygenation: A good filter promotes water movement, which helps transport oxygen throughout the tank. This ensures that your fish have enough oxygen to breathe and maintain a healthy metabolism.
  • Beneficial Bacteria: By providing a surface for these essential microorganisms to grow on, a good filter supports the establishment of beneficial bacteria colonies. These bacteria are vital for breaking down harmful waste products like ammonia and nitrite into less toxic substances, ensuring a balanced and safe environment for your fish.

Having a good filter in your 5-gallon tank is crucial for maintaining water quality, removing waste, providing oxygen, and promoting beneficial bacteria growth.

By ensuring a clean and healthy environment, you can support a thriving ecosystem for your fish, regardless of the number of fish in your tank. Remember, a properly maintained tank is key to both the health of your fish and your enjoyment of your aquarium!

How Many Fish Can a 5-Gallon Tank Hold?

Determining the number of fish you can keep in a 5-gallon tank is crucial as each species requires different space, water, and living conditions. The general rule of thumb is one inch of fish per gallon of water. However, it’s important to remember that this rule doesn’t always apply to all species, different fish have different needs in terms of space and water quality.

When looking at the number of fish, consider these factors:

  • Fish size: The size of the fish affects the amount of space they require for swimming and overall growth.
  • Fish activity levels: Active fish need more space to swim freely, whereas less active fish can thrive in smaller spaces.
  • Fish compatibility: Consider fish species compatibility to avoid territorial or aggressive behavior in the limited space.
  • Water quality: Some fish produce more waste than others, impacting water quality; a crowded tank can lead to unhealthy conditions.

To answer the question directly:

  • For small, less active fish such as shrimp, guppies, and neon tetras, you may keep up to six fish in a 5-gallon tank.
  • If you choose slightly larger or more active fish like bettas or dwarf cories, two to three fish would be suitable for a 5-gallon tank.

Keep in mind that these are just guidelines, and you must always research and understand the specific needs and requirements of the chosen fish species.

What are the Best Fish Species for a 5 Gallon Tank?

When considering the best fish species for a 5-gallon tank, it’s essential to take into account not just the fish size, but also their temperament and activity levels. The following list contains some popular options for stocking your small tank:

  • Betta fish: A single betta fish works well as they don’t require a lot of swimming space and are comfortable being alone.
  • Sparkling gourami: These small, colorful fish are peaceful and an ideal choice for a 5-gallon tank setup.
  • Celestial pearl danio: Active and striking, a small group of these fish can coexist peacefully in your tank.
  • Endler’s livebearers: Known for their vibrant colors, these fish adapt well to smaller tanks and can be kept in a small group.
  • Cherry shrimp: Although not fish, cherry shrimp can add variety to your tank, and their size makes them suitable for a 5-gallon setup.
  • African dwarf frogs: Also not fish, these small aquatic frogs can be an interesting addition to a 5-gallon aquarium.

Keep in mind that overstocking your 5-gallon tank could lead to poor water quality and put stress on the fish, leading to health problems. It’s essential to maintain the ideal environment with proper filtration, temperature, and water parameters.

When in doubt, always consult the professionals at your local aquarium store to ensure the best outcome for your aquatic friends.

How to Stock a 5-Gallon Fish Tank?

When it comes to stocking a 5-gallon fish tank, you’ll want to be very selective about the fish species you choose and the number of fish you introduce. Here is a step-by-step guide on how to stock your tank:

  1. Research fish species: Start by researching the best fish species for a 5-gallon tank. Some good options include Betta fish, small rasboras, and endlers. Avoid choosing fish that grow too large or are territorial.
  2. Choose 1-2 fish species: For a 5-gallon tank, you should limit the number of fish species to one or two types. This prevents overcrowding and ensures that the fish you introduce are compatible with each other.
  3. Consider one centerpiece fish: Rather than having multiple smaller fish in your tank, focus on one centerpiece fish like a Betta. This will give the tank visual appeal without overstocking it.
  4. Introduce shrimp or snails: You can introduce shrimp or snails as tank mates to your fish. They have a low bioload, meaning they won’t contribute significantly to the waste produced in the tank.
  5. Select a few aquatic plants: Aquatic plants help improve water quality and provide shelter for your fish. Stick to plants that thrive in low-light conditions and don’t require complex maintenance, such as Java moss or Anubias.

Here’s a stocking example for a 5-gallon tank:

Quantity Species Type
1 Betta fish Fish
3 Cherry shrimp Shrimp
2 Nerite snails Snails
Several Java moss Plant
Several Anubias barteri Plant

Remember that every tank is unique, and you should adapt your stocking choices based on your tank’s specific conditions and parameters. Monitor the water quality regularly to ensure the health and well-being of your aquatic pets.

What Fish Species Are Not Suited for a 5-Gallon Tank?

There are several fish species that are unsuitable for a 5-gallon tank due to their size, activity level, and social nature. Let’s take a closer look at some of these fish species to better understand why they may not thrive in such a small environment.

  • Goldfish: Goldfish are notorious for being kept in small bowls, but this is actually quite harmful to their health. Goldfish produce a lot of waste and can grow quite large – up to 12 inches – which makes a 5-gallon tank insufficient for their needs.
  • Cichlids: Although there are many types of cichlids, most require at least a 20-gallon tank to accommodate their territorial behavior and social nature. Additionally, some cichlid species can grow up to 6 inches in length.
  • Plecostomus: Commonly known as “plecos,” these large algae-eating fish can grow up to 2 feet long. In addition to their size, plecos produce a significant amount of waste, necessitating a larger tank.
  • Characins: This group of fish includes tetras, which are generally considered suitable for small tanks. However, other characin species like piranhas, silver dollars, and giant hatchetfish require larger tanks due to their size, behavior, and group-living preferences.
  • Loaches: Loaches can get significantly larger and more active than a 5-gallon tank can accommodate. As they usually prefer to live in groups, these social fish would not fare well in such restricted space.

It is important to research the specific needs and behaviors of a fish species before purchasing and placing them into a 5-gallon tank. Many fish require larger tanks, different water parameters, or room for a group of fish in order for them to thrive. Choosing the right species for your tank size will greatly improve the health and happiness of your aquatic pets.

What are the Common Mistakes with 5-Gallon Tanks?

When it comes to maintaining a healthy environment for your fish in a 5-gallon tank, there are several common mistakes that you should avoid. These errors stem primarily from misjudging the capacity of a 5-gallon tank, resulting in overcrowding and other issues that could affect the health and well-being of your fish.

Overstocking the tank: A common misconception is that you can fit a large number of fish in a 5-gallon tank. However, these tanks are suitable for only a few small fish, and overstocking can lead to stress and poor water quality. Make sure to consult guidelines on fish stocking and follow the general rule of 1 inch of fish per gallon of water.

Inadequate filtration: Some people underestimate the importance of proper filtration in a 5-gallon tank, assuming that fewer fish means less waste. In reality, a good filter is critical for maintaining water quality, as fish excrete large amounts of waste that can cause ammonia and nitrite levels to spike. Choose a filter with a flow rate suitable for a 5-gallon tank, and remember to change the filter media regularly.

Skipping water changes: Water changes are essential for maintaining a healthy aquarium environment, even in a small 5-gallon tank. Aim for weekly water changes of 10% to 20% of the tank’s volume to remove waste and replenish essential minerals and trace elements.

Incompatible fish species: It’s crucial to research which fish species are compatible with one another before adding them to your tank. Failure to do so can lead to aggression or competition for resources, causing stress and potential harm to your fish.

Inadequate hiding spots: Many fish, especially small species suitable for a 5-gallon tank, require hiding spots to feel secure. Provide ample cover, such as plants and decorations, to ensure your fish have a safe place to hide and reduce stress levels.

How to Maintain a Healthy 5-Gallon Tank?

To maintain a healthy 5-gallon tank, follow these simple steps:

  1. Regular water changes: Replace 20-25% of the tank water with clean, dechlorinated water every week or two. This will help maintain proper water chemistry and reduce ammonia, nitrite, and nitrate levels.
    • Tip: Using a gravel vacuum during water changes will help remove waste and debris from the substrate.
  2. Monitor water parameters: Check the levels of ammonia, nitrite, and nitrate regularly. These should be 0 ppm for ammonia and nitrite, and under 20 ppm for nitrate.
    • Adopt the right water temperature (76°F to 80°F) by using a heater and thermometer.
  3. Cleaning and maintenance: Remove any algae buildup with an algae scraper or soft sponge, and clean the aquarium glass as needed.
    • Rinse the filter media in old aquarium water during water changes.
  4. Proper feeding: Avoid overfeeding as it can lead to water quality issues. Feed your fish only the amount they can consume within a few minutes, once or twice a day.
  5. Stock compatible fish species: Make sure you have selected fish species that are suitable for a 5-gallon tank and can coexist peacefully.

It’s crucial to maintain a healthy environment in your 5-gallon tank. A well-maintained tank reduces stress on your fish, keeps them healthier, and ensures they live comfortably in their small habitat.

How to Maximize Space in a 5-Gallon Tank?

To maximize space in your 5-gallon tank, consider a few essential tips and techniques. These primarily involve the smart allocation of items within the tank, careful fish selection, and efficient organization of aquatic plants.

  • Choose smaller, compact decorations: Opt for small, space-saving decorations, including rocks, caves, and driftwood, enabling your fish to have more swimming area. Ensure there’s enough room for your fish to move around without encountering any obstacles.
  • Organize aquatic plants efficiently: Select small, slow-growing plants that won’t dominate your tank while offering natural cover and additional oxygen for your fish. Some suitable species include Anubias nana, Java moss, and Dwarf sagittaria. Place them strategically in the tank to create hiding spots and mimic a natural ecosystem.
  • Proper fish selection: Select small, peaceful fish that are comfortable in smaller environments. Some ideal fish species for a 5-gallon tank are Betta fish, Endler’s livebearers, and Cherry shrimp. Avoid large, aggressive, or territorial fish, as they’ll require more space and can lead to an overcrowded tank.
  • Check compatibility: Take fish compatibility into account when deciding how many fish to keep in the tank. Species that can coexist peacefully without stressing each other will help utilize the available space efficiently.
  • Minimize equipment size: Choose small, compact equipment like filters, heaters, and air pumps that consume minimal space within the tank. A useful suggestion is to opt for a sponge filter and an adjustable heater. These equipment types will provide the necessary function for the tank without taking up too much space.

By applying these tips and techniques, you’ll create an efficient, healthy, and spacious environment for your fish in a 5-gallon tank.


Stocking a 5-gallon tank requires careful planning and a good understanding of the needs of your fish species. By following the guidelines and advice we’ve provided in this article, you can create a healthy and thriving aquatic environment. Don’t hesitate to leave a comment and share your thoughts or experiences on stocking a 5-gallon fish tank!

Aquarium   Updated: June 13, 2023
avatar Hello, my name is Fabian, and I am the Chief Editor at Aquarium Nexus. I have over 20 years of experience in keeping and breeding fish. The aquarium hobby brings me immense joy, and I take great pleasure in sharing my experiences with others.

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