Types of Aquarium Fish

Freshwater aquarium fish are diverse, ranging from the peaceful and easy-to-care-for species to the more vibrant and interactive types. Popular choices include livebearers like guppies and mollies, known for their lively colors and ease of breeding. Tetras and danios are excellent for community tanks due to their small size and schooling nature, while bettas offer a variety of colors and fin types, suitable for solitary living.

Cichlids form a large and varied group within freshwater species, with African cichlids from the Rift Valley lakes being particularly colorful and active. In contrast, the larger South American cichlids like oscars and angelfish are known for their individual personalities and more demanding care requirements. Catfish, such as the Corydoras, are favored for their bottom-cleaning habits and are a staple in many freshwater setups.

Saltwater or marine aquariums typically house a stunning array of fish, from the iconic clownfish, which is hardy and beginner-friendly, to the vividly colored tangs and angelfish, which require more extensive care and larger tanks. Saltwater species often demand stable water conditions and a well-maintained environment, making them a more challenging but rewarding choice for the dedicated hobbyist. Wrasses and blennies add personality and pest control to the mix, making them valuable additions to many reef aquariums.

Freshwater versus Saltwater Fish

In the realm of aquarium keeping, you will encounter two primary types of habitats: freshwater and marine (saltwater). Your choice will dictate the fish species you can keep, the care they require, and the overall aquarium setup.

Freshwater Fish

Freshwater fish thrive in bodies of water with a salt concentration of less than 1 part per thousand (ppt). Popular freshwater species include:

  • Catfish: Known for their barbels, which resemble a cat’s whiskers.
  • Cichlids: With a variety of colors and behaviors, ideal for vibrant community tanks.

These species often come from rivers, lakes, and streams, and they generally require simpler aquarium setups compared to saltwater tanks. With a wide range of colorful and resilient species, freshwater aquariums are a good starting point for new aquarists.

Saltwater Fish

Saltwater or marine fish inhabit environments where the salt concentration averages 34-36 ppt. Typical marine species include:

  • Clownfish: Recognizable by their bright orange and white-striping, famous from movies.
  • Tangs: Noted for their vivid colors and sail-like fins.
  • Lionfish: With their striking appearance and venomous spines, they are both beautiful and potentially dangerous.

Setting up a saltwater tank can be more complex and expensive, due both to the sensitive nature of marine life and the need for specialized equipment to maintain water quality and salinity. Yet, for those willing to invest time and resources, a marine aquarium is an incredibly rewarding endeavor, boasting a remarkable diversity of exotic species.

Common Freshwater Fish Types

When setting up your aquarium, choosing the right types of fish is crucial. This section focuses on common freshwater fish types that you can consider for your home aquarium.


Livebearers are popular for their ease of breeding and care. Guppies and mollies are notable due to their vibrant colors and adaptability to different water conditions. They are social fish that do well in groups, though it’s important to manage the male-to-female ratio to avoid overpopulation.


Cichlids are known for their diverse colors and interesting behaviors. African cichlids from the Rift Lakes are particularly sought after for their vivid appearance and active demeanor. South American cichlids like the oscar are larger and can be more territorial, requiring more space and specific water conditions.


Corydoras, or Cory Cats, are peaceful bottom dwellers that are excellent for keeping your substrate clean. Another common type, the Plecostomus, is well-regarded for its algae-eating habits. These catfish are nocturnal and are often seen foraging for food during the night.


Characins include the well-known neon tetra, which is prized for its bright, iridescent colors and schooling behavior. Tetras are best kept in groups within a planted aquarium, which closely resembles their natural habitat and reduces stress.


Loaches, such as the Kuhli loach, are unique due to their elongated bodies and peaceful nature. They require soft substrates and are known to be excellent at controlling snail populations. These fish are typically nocturnal and need hiding spots to rest during the day.


Rainbowfish, like the Boeseman’s rainbowfish, are appreciated for their iridescent coloration that changes depending on the lighting and angle. They are active swimmers and do best in a planted tank that allows them to exhibit natural behaviors.

Popular Saltwater Fish Families

Saltwater aquariums bring a slice of the ocean into your home, showcasing vibrant and diverse fish from several distinct families. Each family offers unique characteristics and habitat requirements that are crucial for their wellbeing in your aquarium.


Surgeonfish are known for their bright colors and distinctive scalpel-like spines near the tail, which is where their name originates from. In your tank, they require plenty of space to swim and a diet rich in algae.


Clownfish are among the most recognizable saltwater fish, usually forming symbiotic relationships with sea anemones. They are hardy and can thrive in captivity, making them suitable even for beginner aquarists.

Damsel Fish

Damsel fish are a hardy group known for their bright coloration and ability to adapt to various tank conditions. However, their aggressive behavior can be a challenge if you plan on a community tank.


Butterflyfish are known for their flattened bodies and intricate patterns. They need a well-maintained tank with plenty of hiding places and a specific diet, which often includes coral polyps and small invertebrates.


Marine angelfish sport a diverse palette of colors and patterns. They require larger tanks with ample hiding spaces and a diet that includes both plant and animal materials to keep their coloration vibrant.


Gobies are small, bottom-dwelling fish that often form symbiotic relationships with burrowing shrimp. They can help maintain your tank by consuming algae and are known for their interesting behaviors and ability to fit in smaller tanks.

Aquarium Size and Fish Types

Selecting the right aquarium size is crucial for the health of your fish and intricately relates to the type of species you can keep.

Nano Tanks

Nano tanks are typically aquariums under 10 gallons. They’re suitable for small species such as Betta splendens (Betta Fish), which thrive in a minimum of 5 gallons. With nano tanks, you must pay close attention to water quality, as smaller volumes can lead to quicker changes in water parameters.

Medium Tanks

Medium tanks, ranging from 10 to 40 gallons, offer more flexibility for fish selection and aquascaping. In this range, you can comfortably keep a community of small to medium-sized fish, like neon tetras or guppies, ensuring they have enough space to exhibit natural behaviors and interact.

Large Tanks

When you’re ready to make a significant long-term commitment, large tanks of 55 gallons or more allow you to explore a wider array of fish species. Large tanks accommodate fish that grow bigger, such as the common goldfish or the striking Arowana, which can require 180 gallons or more as they mature. With larger volumes, maintaining stable water conditions becomes easier, but the initial setup and ongoing maintenance demand more resources.

Fish Temperament and Compatibility

When selecting fish for your aquarium, understanding the temperament and compatibility among different species is paramount. Temperament refers to the general behavior of fish, which ranges from peaceful to aggressive. Peaceful fish like neon tetras or guppies are often more suited to community tanks, while species such as certain cichlids may exhibit territorial aggression.

Compatibility is influenced not only by behavior but also by environmental needs. You should consider water parameters (like pH and hardness), temperature, and fish sizes to ensure cohabitation is stress-free for all aquarium inhabitants.

To assist you in making informed decisions, below is a basic compatibility guide:

Fish Type General Temperament Compatible with Avoid pairing with
Neon Tetra Peaceful Other small, peaceful community fish Large, predatory fish
Guppy Sociable, peaceful Mollies, Platies Aggressive or fin-nipping fish
Cichlids Can be aggressive Same species or similar temperament Small, peaceful fish

Remember, individual fish can have unique personalities, and these are general guidelines. Regular observation of your aquatic pets’ behavior is essential to maintaining a harmonious tank environment.

Care Level and Life Span of Fish Types

When choosing your aquarium fish, it’s crucial to understand the care level and life span associated with each species. Your experience as an aquarist can influence which fish are suitable for your aquarium ecosystem. Some fish demand minimal care and are good choices for beginners, while others may require more complex care.

Angelfish, a common tropical aquarium pet, typically live for over 10 years. They need a well-maintained tank with a stable environment. Conversely, Australian Lungfish are noted for their remarkable longevity, with life spans ranging from 80 to 95 years, necessitating a long-term commitment.

Here’s a summarized list of care levels and lifespans for popular aquarium fish:

Species Lifespan Care Level
Angelfish 10+ years Moderate
Apistogramma 5-10 years Moderate
Archer Fish ~5 years Moderate
Armored Catfish 7-15 years Moderate
Koi Carp 25-35 years High
Goldfish Varies Moderate
Kuhli Loach Not specified Moderate
Rainbow Platy Not specified Easy

Koi Carp, while boasting a life span of 25-35 years, require a significant amount of space and a well-maintained pond or large aquarium. They are omnivorous and have a peaceful temperament, but they are better suited for more experienced hobbyists due to their care requirements.

Beginner-friendly species such as the Rainbow Platy are vibrant and easy to care for, making them an ideal choice for those new to fishkeeping. Remember, the key to maintaining your fish’s health and longevity is providing a clean habitat, proper diet, and monitoring water conditions regularly.

Dietary Needs by Fish Type

When selecting food for your aquarium fish, understanding their dietary needs is crucial to their health. Your fish may be carnivoresherbivores, or omnivores, each with specific feeding requirements.

Carnivores require a diet rich in protein, often satisfied with options like frozen foods, live foods, or specially formulated pellets. Your carnivorous fish should be given foods that mirror their natural diet, which consists of meaty foods such as small fish, worms, or crustaceans.

Herbivores have dietary systems designed to process plant material efficiently. Offer them a variety of vegetables, algae wafers, and plant-based flakes to ensure a balanced diet. Remember to provide foods that sink to the bottom for your bottom-feeding herbivores.

Omnivores benefit from a varied diet that includes both plant and animal sources. Flakes, pellets, and an occasional treat of fresh or frozen foods can provide your omnivorous fish with a balanced diet.

Your fish’s dietary needs also depend on where they feed in the water column. Surface feeders, for example, may prefer flakes that float, while mid-water and bottom dwellers often do better with sinking pellets or wafers. It’s essential to choose the type of food that suits their feeding behavior to ensure they receive adequate nutrition.

To maintain optimal health and coloration, provide a diet that closely matches what your fish would eat in the wild. This may include mixing different food types and routinely changing their diet to prevent deficiencies.