Clownfish like Nemo and goldfish may seem like they would make good tankmates, but in reality they have very different needs when it comes to water conditions, space requirements, and diet. If you’re short on time, here’s a quick answer to your question: Nemo the clownfish needs warm, salty water and plenty of swimming space, while goldfish require cool, fresh water and room to grow much larger than a clownfish.

Housing them together risks health problems or aggression between the two species.

In this nearly 3000 word guide, we will do a deep dive into all the reasons it’s inadvisable to cohabitate clownfish and goldfish. We’ll explore their disparate habitats, growth rates, behavior, ideal water parameters like pH and salinity, potential for disease transmission, and more.

Read on for an extensive look at why Nemo simply can’t live happily or healthily sharing a tank with goldfish.

Natural Habitats of Clownfish vs Goldfish

Clownfish Are Tropical Reef Fish

Clownfish, also known as anemonefish, are a type of fish that live in tropical coral reefs in the Indo-Pacific ocean. They have an iconic appearance with bright orange and white stripes and can grow up to 4 inches long.

Clownfish form a symbiotic relationship with sea anemones and are immune to the stinging tentacles of the anemone. This provides the clownfish protection from predators. Clownfish live in shallow lagoons and outer reef slopes in water temperatures from 72-82°F.

They are found at depths from 0-100 feet. Some well-known species of clownfish include the ocellaris clownfish, tomato clownfish, and false percula clownfish. The movie Finding Nemo featured an ocellaris clownfish named Nemo. Clownfish thrive in their natural habitat of coral reefs.

Goldfish Originated in Temperate Freshwater

In contrast to clownfish, goldfish originated in temperate freshwater environments, not tropical oceans. They are a domesticated version of a carp native to east Asia. Goldfish are thought to have been first selectively bred in ancient China over a thousand years ago.

Their natural habitat is slow moving rivers, ponds, and lakes in temperate climates. Today, wild goldfish are found throughout Asia, Europe, and North America. They prefer water temperatures between 65-75°F. Goldfish can survive in cold water but do best in more moderate temperatures.

Unlike clownfish that stay small, goldfish can grow quite large, up to 1 foot long. Common goldfish come in yellow, orange, and gold colors. Fancy goldfish have been bred for unique shapes and colors like black, white, red, and calico patterns.

Goldfish thrive in temperate freshwater habitats like ponds and lakes.

Size Difference Between Mature Clownfish and Goldfish

Clownfish Stay Smaller

Clownfish, also known as anemonefish, are a type of small fish that live symbiotically with sea anemones. They are native to warmer waters in the Indian and Pacific oceans. Clownfish remain quite small, typically reaching lengths of only 3-4 inches (7-10 cm) as adults.

The common clownfish or Amphiprion ocellaris is one of the smallest species, maxing out at around 4 inches. Some key facts about their petite size:

  • Clownfish have a limited growth rate due to their habitat. Living in anemones restricts how large they can grow.
  • Their small size helps them move around easily in the sea anemone’s tentacles.
  • Being smaller also allows them to hide easily amongst the anemone’s tentacles to avoid predators.
  • As clownfish age, their growth rate slows dramatically after reaching maturity.

Goldfish Grow Much Larger

In contrast to clownfish, goldfish have a reputation for growing quite large given the proper environment. Selectively bred as pond and aquarium fish, goldfish come in many varieties but all share a proclivity for significant growth. Here’s an overview of their size potential:

  • Common goldfish average 12-14 inches long but can reach up to 18 inches in ideal conditions.
  • Fancy goldfish like Orandas and Ranchus grow around 8-10 inches on average.
  • The biggest goldfish on record reached nearly 2 feet long weighing over 4 pounds!
  • With proper space and food, goldfish continue growing throughout their lifespan of 10+ years.
  • Goldfish release growth-inhibiting hormones when crowded, stunting their growth.

Behavioral Differences and Compatibility Issues

Clownfish are Territorial

Clownfish exhibit territorial behavior and will often claim an anemone as their home, aggressively defending it from other fish (The Spruce Pets). As members of the damselfish family, they can be very aggressive towards unfamiliar fish that invade their space.

In a small tank environment, clownfish may constantly chase, nip fins, or even kill fish that are introduced as tankmates.

Part of what makes clownfish good candidates for saltwater community tanks is that they tend to only show aggression within their territory. However, in a cramped space like a desktop tank, the clownfish may claim the entire tank as its territory and frequently terrorize docile species like goldfish.

Goldfish May Be Fin Nippers

While generally peaceful, goldfish will opportunistically nibble on the flowing fins of slower moving species (Pet Keen). Unfortunately, the vibrant fins of a clownfish make for an enticing target. Persistent nipping can lead to nasty infections that may ultimately kill the clownfish.

Goldfish also produce more waste than saltwater species, polluting the water with ammonia, nitrites, and nitrates. Poor water quality stresses fish and further increases aggression and fin nipping tendencies.

Factor Clownfish Goldfish
Territorial Behavior Highly territorial, aggressive to invaders Mostly peaceful, some fin nipping
Ideal Water Conditions Tropical marine Cool, fresh
Waste Production Low High

As the comparison shows, clownfish and goldfish have incompatible housing needs and aggressive tendencies. Attempting to keep them together, especially in a small tank, will likely end disastrously for the fish.

While the behavior and appearance of clownfish and goldfish may suggest they are suitable tankmates, the reality is quite different. Their needs for water quality, temperature, habitat setup and tank size make cohabitation challenging if not impossible.

For their health and safety, Nemo and friends should not share tight quarters with goldfish. Anyone looking to add vibrant saltwater species should set up a dedicated marine aquarium instead.

Water Chemistry Needs

Clownfish Require Warm, Salty Water

Clownfish, also known as anemonefish, thrive in the warm ocean waters of coral reefs. As saltwater fish, they require water with high salinity between 1.022-1.025 sg to survive (Reefs, 2023). The ideal water temperature for clownfish ranges between 75-82°F.

This comfortable water chemistry allows the symbiotic relationship between clownfish and sea anemones to flourish.

Anemones provide clownfish with shelter and protection, while clownfish defend anemones from predators. Both species benefit from the partnership. Without access to sea anemones in a saltwater habitat, clownfish would struggle to survive predators.

Furthermore, the mineral levels in saltwater aid essential bodily functions in clownfish. For example, calcium maintains bone structure, iodine regulates metabolism, and magnesium assists with enzyme production (Saltwater Aquarium Handbook, 2022).

Depriving clownfish of these saltwater minerals over an extended period weakens the immune system, impairs growth and development, and shortens lifespan.

Goldfish Prefer Cool, Fresh Water

In contrast to clownfish, goldfish thrive in cool freshwater between 60-72°F. They originated as a domesticated carp in China over a thousand years ago, bred to tolerate cold climates in outdoor ponds and lakes (AZ Animals, 2023).

Today, most goldfish live in manmade aquariums and remain quite comfortable in still fresh water.

While goldfish can temporarily manage slightly brackish water, salt is toxic if levels grow too high. Max salt tolerance differs by goldfish variety, ranging from 5 grams/liter for common goldfish to 17 grams/liter for Shubunkins (Sustainable Goldfish, 2022).

But in general, salt above 1 tsp per gallon of water (approximately 6 grams/liter) endangers goldfish health.

Additionally, goldfish do not receive any known benefits from salt or other dissolved minerals found in saltwater. Unlike clownfish, their bodily functions developed to extract nutrients from freshwater sources over centuries of evolution.

While goldfish enjoy clean, oxygen-rich water, salt and high mineral content offer no advantages.

Potential for Transmitting Diseases

Keeping Nemo the clownfish with goldfish creates the potential for transmitting diseases between the two species. Here’s why:

Different Immune Systems

Clownfish and goldfish have evolved with different pathogens in their native environments. As a result, their immune systems are equipped to handle different diseases.

For example, clownfish can tolerate coral reef diseases, while goldfish have defenses against freshwater diseases. When kept together, they are vulnerable to illnesses they have no immunity against.

Cross-Species Contamination

Fish release waste and respiratory fluids into the water that can contain viruses, bacteria, fungi, and parasites. If one fish is harboring a pathogen, it can easily spread to fish of other species in the same tank.

For instance, clownfish are prone to Marine Velvet disease, which is caused by dinoflagellates that could be devastating to goldfish. The cross-contamination goes both ways.

Stress Weakens Immune Systems

Even diseases that pose minimal health risks can become problematic when fish are stressed. Stress weighs down the immune system, making fish more vulnerable to pathogens in their environment.

Clownfish and goldfish have very different needs in terms of water conditions, tank decor, diet, and social structures. Trying to accommodate both in the same tank causes chronic stress for one or both species.

For example, clownfish do best in stable water with low nitrates, while goldfish thrive in varied water conditions with higher nitrates. These incompatible needs lead to ongoing stress when the two are tankmates.

Increased Disease Transmission

Besides cross-contamination between species, grouping different fish together also promotes quicker transmission of disease between members of the same species.

Having all fish in one space removes barriers that would naturally separate infected individuals. Especially in aquarium conditions, pathogens pass more readily between tankmates than they would between members of a larger wild population.

While clownfish do live together in the wild, they inhabit a much larger area than a small tank. And goldfish don’t congregate in dense groups in nature at all.

Other Care Differences


Proper nutrition is vitally important for keeping clownfish like Nemo healthy and thriving. Clownfish are omnivores that need a balanced diet of meaty foods like brine shrimp along with spirulina and other algae. They graze constantly throughout the day.

Goldfish, on the other hand, are opportunistic omnivores that will eat flake foods, pellets, veggies, and small invertebrates. They do not need to be fed as often as clownfish and will overeat if given too much.

Here are some key feeding differences between clownfish and goldfish:

  • Clownfish should be fed small meals 3-5 times per day while goldfish only need to be fed 1-2 times per day.
  • Clownfish require a diet higher in protein from meaty foods while goldfish need more fiber and veggies.
  • Clownfish will starve quickly without constant grazing but goldfish can go days without eating.
  • Overfeeding can lead to obesity and swim bladder problems in goldfish but clownfish regulate their food intake well.

Providing species-appropriate diets and feeding schedules is crucial for the health of both types of fish.

Tank Size

Clownfish like Nemo and goldfish have very different requirements when it comes to tank size. In nature, clownfish inhabit coral reefs which provide virtually endless space. But in captivity, a mature clownfish only requires about 30 gallons. They prefer length over depth and ample hiding spaces.

Goldfish, on the other hand, are large fancy carp that can grow over 12 inches long. The general rule is 20 gallons for the first goldfish and 10 gallons for each additional fish. Giant goldfish breeds may need 100+ gallon tanks. Housing goldfish in too small of a tank can cause dangerous stunting.

Here are some key tank size considerations:

  • A 30 gallon tank is sufficient for a pair of clownfish while goldfish need much larger enclosures.
  • Clownfish do well in nano reef tanks while goldfish require room to swim and grow.
  • Overcrowding leads to aggression in clownfish and stunted growth in goldfish.
  • Clownfish tank size depends on anemones and other tankmates while goldfish space requirements are based on individual fish size and number.

Providing adequate room to thrive based on species needs prevents common health issues in both types of fish.

Tank Decor

When it comes to tank decor, clownfish and goldfish have very different enrichment needs. Clownfish require complex saltwater reef environments. They need ample live rock for hiding and hosting anemones, along with substrate and corals.

Goldfish appreciate simple setups with smooth gravel substrate, hardy plants like anacharis or java fern, and a few large decorations. Sharp decor and substrate should be avoided to prevent goldfish injuries.

Some key differences in tank decor preferences:

  • Clownfish need live rock and corals while goldfish do best with smooth gravel and plastic plants.
  • Anemones are essential for clownfish while goldfish may eat or uproot live coral reef species.
  • Clownfish appreciate intricate reefscapes while goldfish need simple decor with open swimming space.
  • Plastic plants and ornaments are unsafe for clownfish compared to goldfish that do not pose digestive threats.

Providing engaging species-specific tank decor enrich the lives of both clownfish and goldfish.


In summary, clownfish and goldfish are incompatible as tankmates due to differences in native environment, adult size, behavior, water preferences, disease susceptibility, and general care needs. While it may seem like a fun idea to house these popular aquarium fish together, Nemo truly can’t thrive sharing a tank with goldfish.

We hope this comprehensive article gave you a deep understanding of all the factors that make clownfish and goldfish a poor mix. When setting up your saltwater or freshwater aquarium, be sure to carefully research compatibility before selecting tankmates.

This will lead to healthier, happier fish that can live full lifespans.

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