What is the Smallest Reef Fish?


What is the Smallest Reef Fish?

When people think of reef fish, they often think of large and showy fish species. But there is a whole class of other fish that do well even in smaller aquariums. So let’s take a look at the smallest reef fish and how to care for these nano reef aquarium fish!

What are Nano and Pico Reef Tanks?

As you’d expect, nano and pico reefs are aquariums at the smaller end of the reef-keeping spectrum. Nano reef tanks are saltwater aquariums 30 gallons or smaller. Meanwhile, a pico reef tank is one 5 gallons or less!

Why Choose Nano Reef Tanks?

Nano reef fish are usually less expensive than larger reef aquarium fish since they are so small. Yet most of your choices are still vibrant fish, just like other reef animals. A nano reef tank also costs significantly less to both setup and maintain. Just be aware that there are also downsides to smaller nano reef systems.

Are Nano Reef Tanks Hard to Keep?

A nano reef tank is not a saltwater aquarium for absolute beginners. In fact, they are more challenging than larger saltwater tanks. Nano aquarium (and pico reef tank) setups can shift in parameters faster than a larger fish tank.

Such a small aquarium will respond fast if leftover food or a dead fish decays into ammonia. A power outage will cause the water to cool faster. Evaporation will increase salinity faster. And so on.

You need to be very good at maintaining reef fish and coral water conditions. These animals thrive with stability. Remember, the conditions of the ocean hardly change over even thousands of years.

Also, there are not as many fish for nano reef aquarium setups. Most popular saltwater fish species tend to be medium-sized fish or larger. They need tanks larger than 30 gallons in volume.

Nano Reef Tank Saltwater Fish

What if you don’t want larger reef fish and want to try smaller saltwater aquariums? Think about trying some of these reef-safe fish sized for nano tanks.

Royal Gramma

The Royal gramma is a peaceful and small saltwater fish from the Caribbean Sea. Growing no larger than 3 inches they are an ideal nano reef tank inhabitant.

They are carnivorous, feeding on brine shrimp and other small invertebrates. And while a Royal Gramma will spend most of its time out in the open. But they do need caves and other hiding places to retreat to.

Grammas can be aggressive fish if they have to compete with their tank mates for places to hide. So provide plenty of hiding spaces for everyone. They are also aggressive towards their own species. So only keep one gramma per nano tank.

  • Scientific Name: Gramma loreto
  • Origin: Caribbean Sea
  • Length: 3 inches
  • Tank Size: 30 gallons

Six Line Wrasse

Six Line Wrasses are striking fish, with purple and orange horizontal stripes running along their flanks. They may look delicate but these wrasses are hardy fish and long-lived as well: up to 10 years in captivity.

The Six Line Wrasse is reef safe and won’t bother corals. But they do eat small invertebrates so keep them away from tiny shrimp and hermit crabs. Larger shrimp (like Coral Banded shrimp) won’t be molested, however.

Also, be aware that Six Line Wrasses are not timid fish. They can be aggressive towards other tank mates, nipping at fins and competing for food. Keep them with fish that can defend themselves like Grammas, Pygmy Angelfish, Damselfish, and Tangs.

  • Scientific Name:
  • Origin: Indo-Pacific Ocean
  • Length: 3 inches
  • Tank Size: 30 gallons

Neon Goby Fish

Neon gobies are from the Atlantic Ocean, where they perform the same services as the better known cleaner wrasse. These gobies will sit on coral perches and wait for large fish to come by.

They then pick parasites from their skin, gills, and even their teeth. Being such small fish, neon gobies are great additions to a small nano aquarium. They eat prepared foods and frozen foods with equal gusto.

Neon gobies are peaceful fish and will live in the same aquarium with each other. A bonded male/female pair may become a little territorial, however.

  • Scientific Name: Elacatinus oceanops
  • Origin: Atlantic Ocean
  • Length: 1.5 to 2 inches
  • Tank Size: 10 gallons

Ocellaris Clownfish


Also known as the false percula clownfish, the ocellaris clownfish is one of the most popular and interesting fish in the saltwater hobby.

Ocellaris clownfish live in symbiotic relationships with sea anemones. Anemones can be a little challenging to keep. They need excellent water quality and ample lighting of the right spectrum. But you can keep clownfish in community saltwater tanks without one.

Clownfish are poor swimmers when they don’t have an anemone to hide in, though. So make sure your water currents are gentle enough for them to get around.

  • Scientific Name: Amphriprion ocellaris
  • Origin:
  • Length: 3 inches
  • Tank Size: 20 gallons

Coral Beauty Angelfish

The coral beauty angelfish is a species of pygmy angelfish, staying much smaller than most of their larger cousins. Angelfish are grazers, feeding on sponges, algae, and other encrusting organisms.

Coral beauties may pick at some species of corals. So long as they are well fed, however, pygmy angelfish are mostly reef-safe.

The coral beauty angelfish is at the very limit of what we would consider a nano fish. While they will live comfortably in a 30-gallon tank they may become aggressive towards very peaceful fish.

Keep coral beauties with semi-aggressive tank mates unless the tank is more spacious.

  • Scientific Name: Centropyge bispinosa
  • Origin: Indo-Pacific Ocean
  • Length: 3-4 inches
  • Tank Size: 30+ gallons


Chalk Basslet

Believe it or not, the chalk basslet is a true bass; its family includes the giant grouper and other fish far too huge for your tank! These little bass doesn’t grow larger than 3 inches.

Chalk basslets are also predatory fish. But they only eat small fish fry and shrimp.

The chalk basslet is a peaceful saltwater fish and ideal for smaller reef setups. These inexpensive and very hardy fish have delicate pink and purple tones. Chalk basslets also live together in harmony.

  • Scientific Name: Serranus tortugarum
  • Origin: Caribbean Sea
  • Length: 3 inches
  • Tank Size: 20 gallons


Nano fish species are perfect for aquarists that are space-limited and don’t want a larger setup. Nano fish are often just as colorful as other marine fish. And they tend to cost quite a bit less, as does the aquarium setup. So long as you can maintain stable water conditions in a small setup, nano reef tanks are a great choice for most aquarists!


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