Fish Keeping and Breeding

Top Nano Saltwater Fish For A Nano Reef Aquarium

Written by Jakob

Last Updated on February 13, 2023 by Jakob

Best Nano Aquarium Fish

Nano Saltwater Fish are ideal for small aquariums of 40 gallons or more. An aquarium is considered a nano tank when it’s about 40 gallons. Some definitions will state aquariums defined as ‘Nano reefs’ a lot smaller than that, but it’s a real shame to keep them in anything smaller. Since reef tanks are usually kept by passionate and professional reefers that know what they’re doing (check out for a great community), most people won’t approve of keeping such beautiful fish in a tiny aquarium, and neither do we. Therefore we don’t endorse keeping saltwater reefers in anything less than 40 gallon tanks.

What’s great is that many of these species develop tiny territories within their new fish tank. While they don’t require any specific feeding, we recommend using live rock. That will provide better filtration in a small tank that can easily pollute and also further food source. Small reef aquariums look easy to maintain, but they are still a lot of work!

As I’ve already hinted at, a smaller tank is much more sensitive to pollutants, which is why I recommend live rock. I actually get my live rock from amazon (crazy)! Check our live rock and how to use it article for more info. If you have a larger tank or are more experienced check out our article on the best saltwater fish for an advanced fishkeeper.

Because the tanks are so small, there isn’t enough water to balance out pollutants, and so they become potent. If you’re diligent though, you can still make you tiny tank into a nano powerhouse. Make sure you have a super filter in your nano tank! Make sure you have the right sand for your reef tank as well, as it helps to create a more natural tank.

Be sure to check incompatibilities before purchasing Nano fish. Some small fish, like short men, suffer from short man syndrome and are aggressive toward other fish!

We love the small saltwater fish, so we’ve compiled a list of our 10 favorite saltwater nano fish, for your nano aquarium tank:


Top Nano Saltwater Fish:

1. Pajama Cardinalfish

pajama cardinalfish nano fish tank
Pajama Cardinal Fish get to be about 3 inches (8 cm) in size so that’s the large scale for a nano tank. If you have a 30 gallon tank then these little beauts are ideal. They are not fussy eaters, and are relatively peace loving creatures. They are reasonably priced and generally take a long time to reach full size, especially when in a smaller sized tank.

2. Blue Devil Damsel Fish

yellowtaildamselfishBlue Devil Damselfish – these little guys are on the smaller side of nano fish, which is great, however, they can be very territorial and aggressive. If you do have them – make sure you research their compatibility with other fish and try to limit numbers of males.

3. Blackray Goby

Blackray goby

Also known as the Hi Fin Red Banded Goby, this fish is native to the Philippines and is ideal for nano reef tanks of 10 or more gallons. 

It is a beautiful fish with a silver white coloration and distinct dark stripes on its body and has a yellow face. They grow to 2 inches in length and like plenty of live rock and a sandy bed.

It is not an aggressive fish, so is ideal for nano tanks. It may share its burrow with other species, and they will also form a symbiotic relationship with a pistol shrimp which is very cool to see. 

It is territorial, so may have a go at conspecifics (other members of its species) occasionally, especially if not in a mating pair. 

Photo Credit: Sam Davies (WikiCommons)

4. Neon Blue Goby

Neon Blue Goby

Sometimes known as the “cleaner fish”, neon gobies look a lot like Cleaner Wrasse, and are very mild mannered. They are fast swimming, but don’t distract or irritate other fish. The Neon Blue Goby, or Neon Goby, is known for its stunning ocean blue racing stripes. These signature stripes begin jsut above the eyes and continue down the length of the entire fish. The Neon Blue Goby is one of the hardiest ocean fish and due to its small stature (only 2 inches long) it makes the prefect addition to smaller nano reef tanks.

5. Coral or Crown Goby

crown goby for small nano fish tank

The Yellow Clown Goby is a delightful addition to any saltwater aquarium. Bright yellow and peace loving, they often take shelter in rocks and coral. They can also be active fish, swimming in the open or playing with other fish. A fully grown adult yellow clown goby will reach a minute 1 to 1.5 inches in size, making it perfect saltwater Fish for a nano reef aquarium.

Small but tough, it’s stocky build and strong fins ensure it isn’t a target for larger species.

6. Firefish Goby


The firefish goby is a great nano saltwater fish. It has powerful colors, with a pure white head and an amber red rear. It has a long distinctive fin on the top. Known to have lots of personality, the mild mannered fish is great for its ability to get along well with other species. Only growing up to a couple of inches, the small size and mannerisms make it a top choice for nano reefs.

In its natural habitat, the Firefish goby sticks to small groups just above reefs. They primarily feed of debris and plankton that drift over the reef. Remember, this is very much a reef fish and you’ll need to work hard to provide a safe habitat. Live rock plants and coral are essential. Also, these fish like multiple places to hide, which is best achieved by having the former.

Photo Credit: Drriss & Marrionn

7. Court Jester Goby

court jester goby

The court jester goby originates in the western pacific. Sometimes known as a rainford’s goby, the small fish is timid and peaceful. You’ll need blankets of plants and coral to provide shelter as they are easily startled.

We don’t like ever putting reef or saltwater fish into aquariums without coral, live sand, plants and live rock. In fact, we always have all 4. By definition, that’s their habitat, if you have open ocean fish, then by definition you’ll not have enough space for them to swim.

8. Royal Gramma

royal gramma fish

A striking fish with a rainbow color, this fish hides away within coral and rocks and is aggressive towards its own species. It should be very at home in a nano reef due to its small size.

They are very calm around other fish and won’t cause any problems – just house it on it’s own, or with a mating pair.

It will need lots of room, even though it’s a small fish. Don’t house this little guy in anything less than 35 gallons. They have a very meat heavy diet of crustaceans and shrimp (mysis). That adds to pollutants and is another reason to keep this to larger end of nano reefs.

9. Blue & Green Chromis

blue chromis

The Blue Green Reef Chromis is very easy to look after and is a very common starter fish toe beginners. It’s a beautiful fish, quiet and peace loving.

Blue and green chromis both reach sizes around 4 inches, so that might be too large for most nano fish tanks. Please ensure you have suitable space otherwise keeping it will be a cruel and depressing experience for the fish.

10. The Two Spot Goby

The two spot goby, also known as the crabeye gody, is a striking fish, with large dorsal fins marked by large eyes. White and orange, this fish is generally very gental, having the eyes to ward off predators as its main defense. However, it can become aggressive towards other gobys, unless they are a male/female pair.

It should reside in a 10 gallon or larger aquarium with live sand as a substrate, and plenty of areas to hide. It will eat a variety of live feed, such as brine shrimp.

11. Ocellaris Clownfish


When you think of a coral reef, the first fish you’ll probably think of is the clownfish. Made famous by Finding Nemo, these hardy creatures are the perfect starting addition to any nano reef tank.

With their bright orange coloration with white bands outlined in black, these saltwater reef fish are very striking to watch. They can be kept with or without an anemone host, but if they are attached to an anemone they will become territorial and a more aggressive. 

They get to three inches in length, and are suitable for nano reef tanks of 20 gallons or larger. Some people say they can be in smaller tanks, but be careful with this as you don’t want them to feel cramped.

Make sure to buy a captive bred Clownfish. 98% of wild caught cownfish don’t survive the first year after being caught. So captive bred will not only not damage the natural environment, but they are far hardier and more colorful than any that are wild caught. Read our article on common captive clownfish myths if you don’t believe us!

Thanks to Aeryn for commenting that the sale of wild caught clownfish is now a lot less common place. While that is true, people capturing clownfish from their native coral reefs (including in Hawaii and other US reefs) for the purpose of fish keeping is more prevelant that one might think, and makes it all the more important to highlight that we should do all we can to ensure people buy captive bred, not buy or catch wild clownfish.

Other Mentions:

There are also many different small invertebrates that are ideal in a Nano tank. They include cleaner shrimps, saltwater snails. Hermit crabs are difficult because they need new shells, so please don’t limit them to a small tank, unless you plan on leaving lots of empty shells about.

Here’s some extra tips of choosing nano saltwater aquarium fish:

  • Make sure you ask about maximum fish size – some nano fish will outgrow your tank
  • Some reef fish need live rock, coral and live food to survive. If you only plan on having a basic saltwater tank, then some fish won’t be an option

I hope you’re able to get started on a great nano reef tank!

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