Choosing Compatible Fish for Your Aquarium - WaterWonderLogs (2024)

I recently delved into the fascinating world of aquarium fish, seeking answers to the age-old question: which fish can live harmoniously together in one tank? With so many breathtaking species to choose from, it can be overwhelming to ensure compatibility among them. As I explored this topic, I discovered essential guidelines and insights that will help any aquarium enthusiast create a vibrant, thriving underwater community. By considering factors such as size, temperament, and environmental preferences, you can build a harmonious and visually stunning aquarium that delights both the fish and their human admirers.

Having an aquarium can bring so much joy and relaxation to your life. Whether you’re a seasoned hobbyist or just starting out, one of the most important aspects of maintaining a successful aquarium is choosing compatible fish. When fish are compatible with each other, they can peacefully coexist and thrive in their aquatic habitat. In this article, I will guide you through the process of choosing fish based on tank size, water temperature and pH, fish behavior, swimming levels, feeding requirements, compatibility charts, schooling fish, community fish, compatibility with invertebrates, and avoiding overstocking.

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Consider Tank Size

When it comes to selecting the right fish for your aquarium, the first thing you should consider is the tank size. Different fish require different amounts of space to live happily. Here are three categories based on tank size:

Small tanks

If you have a smaller tank, there are still plenty of fish options that can thrive in limited space. Some popular choices for small tanks include Betta fish, guppies, and tetras. These fish are small in size and can comfortably live in tanks as small as 5 gallons.

Medium tanks

For those with medium-sized tanks, you have more flexibility in your fish selection. Some great choices for medium tanks include Molly fish, dwarf gouramis, and angelfish. These fish require tanks ranging from 10 to 30 gallons to ensure they have enough space to swim freely.

Large tanks

If you have the luxury of owning a large tank, your options are virtually limitless. Large tanks provide ample space for bigger fish and allow for more variety in species selection. Some popular choices for large tanks include cichlids, discus fish, and arowanas. These fish require tanks that are 50 gallons or larger to create a suitable environment for them to thrive.

Water Temperature and pH

Maintaining the proper water temperature and pH level is crucial for the health and well-being of your fish. Different species of fish have specific water temperature and pH requirements. Here are two categories based on water conditions:

Cold-water fish

If you prefer to keep your aquarium at a cooler temperature, there are several cold-water fish species to choose from. Goldfish, koi, and white cloud mountain minnows are popular choices for cold-water aquariums. These fish can tolerate water temperatures between 50 to 72 degrees Fahrenheit and prefer a pH level around neutral (7).

Tropical fish

If you want to create a vibrant and colorful aquarium, tropical fish are a fantastic option. Tropical fish thrive in warmer water temperatures, typically ranging from 76 to 82 degrees Fahrenheit, and prefer a slightly acidic to neutral pH level. Some popular tropical fish species include neon tetras, guppies, and swordtails.

Fish Behavior

Understanding fish behavior is essential when selecting compatible fish for your aquarium. Some fish species are aggressive and may bully or harm other peaceful fish. On the other hand, some fish are peaceful and prefer living harmoniously with their tankmates. Here are two categories based on fish behavior:

Aggressive fish

If you have aggressive fish in your aquarium, it’s crucial to choose tankmates that can hold their own. Species such as tiger barbs, red-tail sharks, and convict cichlids are known for their territorial behavior. It’s advisable to avoid keeping multiple aggressive fish together unless you have a large aquarium with ample hiding spots and territory boundaries.

Peaceful fish

For a serene and tranquil aquarium, peaceful fish are the way to go. Peaceful fish species are known for their calm temperament and ability to coexist harmoniously with other fish. Some popular peaceful fish include danios, platies, and angelfish (in the absence of aggressive tankmates). These fish can create a peaceful community tank where they all thrive together.

Swimming Levels

Fish occupy different swimming levels within the aquarium, which can create a visually appealing and dynamic tank. Understanding the swimming levels of fish is essential when choosing compatible tankmates. Here are three categories based on swimming levels:

Top-dwelling fish

Top-dwelling fish are known for occupying the uppermost level of the aquarium. These fish are great for adding movement and visual interest to your tank’s surface. Some popular top-dwelling fish include hatchetfish, gouramis, and killifish. Keep in mind that these fish require adequate surface area and access to open air for proper breathing.

Middle-dwelling fish

Middle-dwelling fish occupy the middle section of the aquarium. They swim energetically in open water, creating a vibrant and lively atmosphere. Some excellent choices for middle-dwelling fish include tetras, rasboras, and barbs. These fish prefer swimming in schools, so it’s advisable to keep them in groups rather than solitary.

Bottom-dwelling fish

Bottom-dwelling fish are especially fascinating to observe as they occupy the lower portions of the aquarium. They tend to search for food and explore the substrate. Popular bottom-dwelling fish include corydoras catfish, loaches, and gobies. These fish play a crucial role in maintaining the cleanliness of the tank by scavenging for leftover food and detritus.

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Feeding Requirements

Fish have varying feeding requirements based on their diets. Some fish are herbivores and primarily eat plants, while others are carnivores and rely on a meat-based diet. Many fish fall into the middle category of being omnivores. Here are three categories based on feeding requirements:


Herbivorous fish require a diet primarily consisting of plant matter. They thrive on foods such as algae wafers, vegetables, and specially formulated herbivore pellets. Some popular herbivorous fish include certain species of plecos, mollies, and some cichlids. It’s important to provide a balanced diet that meets their nutritional needs.


Carnivorous fish are natural predators and rely on a diet rich in protein from meat sources. They feed on small live or frozen prey, such as bloodworms, brine shrimp, or even small fish. Popular carnivorous fish include bettas, oscars, and pufferfish. It’s crucial to ensure they receive a varied diet to support their overall health.


Omnivorous fish have a diverse diet that includes both plant matter and meat-based foods. They enjoy a varied menu of pellets, flakes, frozen foods, and live foods. Many popular aquarium fish species fall into this category, including angelfish, guppies, and tetras. A balanced diet is essential to meet their nutritional needs.

Compatibility Charts

Compatibility charts are a valuable tool to assist in selecting fish that have similar requirements and behaviors. They provide a quick reference guide to identify potential compatibility issues or suitable tankmates based on specific fish species. There are two types of compatibility charts:

Freshwater fish compatibility chart

A freshwater fish compatibility chart helps determine which species can live harmoniously in the same freshwater aquarium. It takes into account factors such as aggression levels, size compatibility, and swimming levels. It’s advisable to consult a comprehensive compatibility chart when planning your aquarium population to ensure a peaceful coexistence among your fish.

Saltwater fish compatibility chart

A saltwater fish compatibility chart serves as a guide for selecting compatible fish species for a saltwater aquarium. It considers factors such as aggression levels, reef compatibility, and territorial behavior. Saltwater aquariums are generally more complex, and careful consideration of compatibility is vital to maintain a thriving and balanced ecosystem.

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Schooling Fish

Schooling fish, also known as shoaling fish, are fish species that naturally form tight-knit groups in the wild. Keeping schooling fish in your aquarium can create a visually stunning and behaviorally interesting display. Here are three popular schooling fish:


Tetras are small, vibrant fish known for their schooling behavior. Species like neon tetras, cardinal tetras, and ember tetras are popular choices for community aquariums. When housed together in a school, they exhibit synchronized swimming patterns that are mesmerizing to watch. Tetras are peaceful fish that can be kept with other peaceful species.


Rasboras are another excellent choice for creating a stunning school of fish. Harlequin rasboras, chili rasboras, and galaxy rasboras are just a few examples. These fish have beautiful colors and move gracefully in a school. Keeping them in a group enhances their natural behavior and creates a captivating focal point in the aquarium.


Barbs are lively and active fish that thrive in a school environment. Tiger barbs, cherry barbs, and rosy barbs are commonly chosen for community aquariums. Schooling helps reduce aggression in barbs and allows them to display their natural schooling behavior. Keeping barbs in a school also provides them with mental stimulation and a sense of security.

Community Fish

If you’re looking to create a harmonious community aquarium with a mix of fish species, there are several compatible options to consider. Here are three popular community fish species:


Guppies are well-known for their vibrant colors and peaceful nature, making them ideal community fish. They are social and can live peacefully with a variety of other fish species. Guppies are also known for their breeding abilities, so be prepared for a potential population explosion if a male and female are present.

Corydoras catfish

Corydoras catfish, often referred to as “Cory cats,” are bottom-dwelling fish that are excellent community options. They are peaceful, social, and can be kept in groups. Cory cats help keep the substrate clean by foraging for food, providing an added benefit to the overall cleanliness of the aquarium.


Swordtails are lively and attractive fish that thrive in community setups. They are known for their signature elongated tail, resembling a sword. Swordtails are peaceful and can coexist with other peaceful fish, provided they have adequate swimming space and hiding spots. They are also livebearers, so expect them to reproduce if both males and females are present.

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Compatibility with Invertebrates

Alongside fish, many aquarium enthusiasts enjoy introducing invertebrates into their tanks. Invertebrates such as shrimp and snails can add beauty, diversity, and helpful duties to an aquarium. It’s important to choose fish species that are compatible with these invertebrates to ensure their safety. Here are two categories based on compatibility with invertebrates:

Fish and shrimp

Shrimp, like cherry shrimp and amano shrimp, can be fantastic additions to your aquarium. However, it’s essential to choose fish species that won’t prey on or harm these delicate crustaceans. Fish species such as guppies, neon tetras, and otocinclus catfish are generally considered safe tankmates for shrimp.

Fish and snails

Snails, such as mystery snails and nerite snails, are excellent cleaners and algae eaters in the aquarium. However, some fish species may view snails as a tasty snack or actively disturb them. Choosing peaceful fish species like dwarf gouramis, platies, and corydoras catfish ensures a safe environment for snails to thrive.

Avoiding Overstocking

Overstocking an aquarium can lead to numerous issues, including poor water quality, stress for fish, and increased aggression. It’s important to consider territorial behavior and the capacity of your tank when selecting fish. Here are two considerations to avoid overstocking:

Calculating tank capacity

Before adding fish to your aquarium, it’s crucial to calculate the maximum capacity your tank can support. Factors such as tank size, filtration capacity, and species’ adult size play a significant role. It’s generally recommended to avoid exceeding 1 inch of adult fish per gallon of water as a rough guideline.

Considering territorial fish

Some fish species are highly territorial and require ample space and hiding spots. It’s important to consider the territorial behavior of the fish you intend to keep. By providing appropriate habitat and respecting their space requirements, you can minimize stress, aggression, and territorial disputes within your aquarium.

In conclusion, choosing compatible fish for your aquarium is essential for creating a healthy, peaceful, and visually stunning environment. By considering factors such as tank size, water temperature and pH, fish behavior, swimming levels, feeding requirements, and compatibility charts, you can select fish that will thrive together harmoniously. Whether you prefer a vibrant community tank or a specialized setup, thoughtful fish selection will ensure a successful and enjoyable aquarium experience. Happy fishkeeping!

Choosing Compatible Fish for Your Aquarium - WaterWonderLogs (5)

Choosing Compatible Fish for Your Aquarium - WaterWonderLogs (2024)


How do I choose the right fish for my aquarium? ›

Understanding the specific care requirements of fish species is essential for their well-being. Consider factors such as water temperature, pH level, and hardness, as well as any specific dietary needs. Make sure the fish you choose can thrive in the conditions you can provide or are willing to create in your aquarium.

How can you determine what kinds of fish can live together? ›

Schooling species do best in quantities of five or more. These include rasboras, danios, cory cats and more. Semi-Aggressive Fish - As their name suggests, these may bully smaller tank-mates, so aim for an aquarium of fish all close to the same size.

What kind of fish can be in the same tank together? ›

Popular community fish species include Guppies, tetras, danios, rasboras, some barbs, rainbowfish, Bristlenose catfish and Corydoras catfish.

What fish are on the best choices list? ›

The Dietary Guidelines for Americans states that to consume those higher amounts, children should only be fed fish from the “Best Choices” list that are even lower in mercury – these fish are anchovies, Atlantic mackerel, catfish, clams, crab, crawfish, flounder, haddock, mullet, oysters, plaice, pollock, salmon, ...

How many fish can you put in a 20 gallon tank? ›

It is generally recommended to have a maximum of 1 inch of fish per gallon of water. This measurement does not include the tail, but refers to the "adult" size of the fish.

Which aquarium fish has the longest lifespan? ›

Topping the longevity list is one of the most popular aquarium species. Goldfish are extremely resilient, which is why they're often recommended to beginners, and some of them have lived longer than their average 25-year lifespan. In the Guinness Book of World Records, you can find a goldfish that lived for 45 years.

How many fish can you keep together? ›

A common guideline is 1 inch of fish per 1 gallon of water, but not all aquarium specialists agree with this rule.

How many fish can you put in a 10-gallon tank? ›

Water chemistry can be more volatile and influenced easier in smaller tanks compared to larger tanks. In a small 10-gallon tank you should house 6-8 fish, depending on fish size. Many filters are available can be used for small tanks and provide enough mechanical filtration to ensure healthy water for your fish.

How many tetras can you put in a 10-gallon tank? ›

Depends on how planted the tank is. I would do 15 with a semi planted tanks. But make sure to stay up on water changes. Remember no less than 6, it will stress them out.

Can you mix different fish together? ›

Avoid mixing species that are incompatible, as this will lead to aggressive behaviour, stress, and the loss of your fish. The chart below can be used as a basic guide to compatible fish groups and will also help you to identify which groups of fish should not be mixed.

Can you mix different fish in a tank? ›

Choosing the Right Type of Fish

Some types of fish can also not mix, particularly if they are prone to nipping or being nipped. Always check if the type of fish you would like to add to your tank is suitable to mix before introducing them, your aquatic specialist should be able to advise on this.

Can you put 2 female fish together? ›

Unlike male betta fish, female betta fish can live together comfortably in the same tank. When they live together, the cohort is called a 'sorority'. Generally, a good number to keep together is 4-6 female betta fish.

How many fish should you start with in a tank? ›

The most widely known rule for stocking a tank is the one inch of fish per one or two gallons of water rule.

How many fish should a beginner have? ›

In most cases, only two or three fish should be introduced to a tank initially. Once the nitrogen cycle is established and the tank is stable, additional fish can be added each week. However, the same rule applies when adding the next round of fish. Moderation: you must add only a few at a time.

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