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Reef Safe Fish for a 55 Gallon Tank?

‘Reef safe’ aquarium fish are those that not only survive but thrive in a marine tank with corals or live rock. If you’re an intermediate aquarist, you may be looking to upgrade from a small 30-gallon tank (which is great for beginner hobbyists) to a 55-gallon version and are wondering which species of fish can be kept in a medium-sized aquarium with a reef setup?

A 55-gallon reef tank is perfect for a pair of medium-sized fish or a group of 3 to 4 small schooling fish. Consider ‘dwarf’ species of saltwater angels, blennies, clowns, chromises, damsels, dottybacks, gobies and wrasses to add both color and life to your marine tank. Juvenile eels and sharks can also be kept in a 55-gallon tank, albeit temporarily.

Now that you know what kinds of fish you can keep in a 55-gallon reef tank, let’s explore this topic further. We’ll discover which species (in particular) are best for a medium-sized aquarium, how many you can have at a time, and how to choose the best tankmates. We’ll also learn if you can keep a shark in a 55-gallon reef tank and what other creatures besides fish can be kept in a medium-sized aquarium.

So, if you’re ready to learn more about stocking a 55-gallon reef tank, then let’s get started!

What Saltwater Fish Can I Put in a 55 Gallon Reef Tank?

The ‘top 10’ best saltwater fish for a 55-gallon reef tank include:

Bicolor Angels

Bicolor angels are a dwarf species and a good choice for a 55-gallon reef tank. They reach a full-grown length of 4 to 6 inches which is why you should only keep one in a medium-sized tank. Bicolor angels can get aggressive with other species of angelfish so consider housing them ocellaris clownfish instead.

Ocellaris Clowns

A pair of 4-inch ocellaris clownfish is perfect for a 55-gallon reef tank. This species is vibrant, active, and easy to care for. They get along well with other medium-sized fish of similar size and temperament (like bi-color or flame angelfish) but form the best and astrongest bonds with others of their kind.

Six-Line Wrasses

Six-line wrasse fish are a colorful and peaceful dwarf species. Their gentle nature makes them ideal for almost community tank environment. A 55-gallon reef setup can easily house a pair of six-line wrasses. Other possible tankmates include ocellaris clowns, banggai cardinals, and blue-green chromises.

six line wrasse

Green Mandarin Gobies

Green mandarin gobies are beautifully colored and a joy to observe. This peaceful species is perfect for a 55-gallon community tank with other gentle-natured fish. They grow to lengths of around 4 inches so a male-female pair would do quite nicely in a medium-sized tank with ocellaris clowns or blue damsels.

Spotted Mandarin Gobies

Spotted mandarin or target mandarin gobies are peaceful and vibrant with dotted shades of orange, blue, black, and green. Since adults can grow up to 4 inches in length, a mated pair can be kept in a 55-gallon tank with 3 or 4 other fish of like size and temperament like blue damsels or ocellaris clowns.

Royal Dottybacks

Royal dottybacks are bicolored – half purple and half yellow. This active and peaceful fish stays relatively small (around 2 to 3 inches long) so a group of 4 could easily be kept in a 55-gallon tank. A great choice for a tank with blue-green chromises, just don’t keep them with clownfish as they’re likely to get bullied.

Strawberry Dottybacks

Strawberry dottybacks are a bright shade of fluorescent purple. These small, active fish add color and life to any reef tank. For a 55-gallon tank, a group of 3 to 4 is recommended. Though peaceful in nature, they don’t do well with other dottybacks like royals so keep them with blue-green chromis fish instead.

Blue-Green Chromises

Blue-green chromis fish won’t damage corals which makes them perfect for a medium-sized reef tank. This species is non-aggressive and can usually live peacefully with dottybacks and blennies in community tank environment. Reaching a maximum length of 4 inches, 4 to 6 will do well in a 55-gallon tank.

Yellowtail Blue Damsels

Yellowtail blue damsels are a dwarf species and well-suited for a 55-gallon reef tank. They’re the least aggressive of their kind, making them a good choice for a community tank with ocellaris clowns or bicolor angels. They grow to lengths of 3 inches so at least 4 can live comfortably in a medium-sized tank

yellow tail blue damsel

Scooter Blennies

Scooter blennies are an active and unique looking bottom-dwelling fish. They’re ideal for a 55-gallon reef tank since they don’t get much bigger than 4 inches and stay ‘out of the way’ of other marine fish. Basically, any fish that stays in the middle of the tank can live harmoniously with scooter blennies.

**For more options on stocking a 55-gallon reef tank, check out my article entitled Reef Safe Fish for a 30 Gallon Tank since almost any fish that can survive in a smaller tank will thrive in a bigger one! Just make sure the species you choose are peaceful and compatible in a contained environment…

How Many Fish Can I Put in a 55 Gallon Reef Tank?

The general ‘rule-of-thumb’ when it comes to stocking a fish tank is 1-inch of fish per gallon of water. However, you must consider both the behavior and temperament of the fish as well, not just the size. Personally, I think this calculation can easily lead to an unhealthy, overstocked aquarium. A better ratio is 1-inch of fish to every 2.5 gallons of water, minimum.

For a 55-gallon marine tank, I’d suggest no more than 12 total inches of fish – three 4-inch or two 6-inch fish, for example – since most reef fish require plenty of space to claim their territory and/or establish an area in the tank to call ‘home’. This also gives them the extra room they need to swim about freely and explore their aquatic surroundings safely.

Besides Fish, What Other Creatures Can be Kept in a 55 Gallon Reef Tank?

Fish aren’t the only aquatic creatures that can be kept in a 55-gallon reef tank. Marine invertebrates like shrimps and snails can also thrive in a medium-sized reef tank. The best options include ghost shrimp, peppermint shrimp, and harlequin shrimp as well as nerite snails. If you want to add cleaner shrimp, no more than two should be kept in a 55-gallon tank at any given time.

Crustaceans like crabs can also be kept in a medium-sized reef tank. Peaceful species like hermit crabs, emerald crabs, and anemone crabs are recommended. Regarding a 55-gallon reef tank, use the ‘one crab per every 5 gallons of water’ rule. If you plan to keep an aggressive species like arrow crabs, make sure to keep just one since they won’t tolerate other of their kind and will attack smaller shellfish.

Can You Keep an Eel in a 55 Gallon Tank?

The snowflake eel, for example, is a great choice for intermediate saltwater aquarists looking to add a few ‘showpiece’ fish to their 55-gallon reef tank. Because this species can reach full-grown lengths of 24 inches, only a single juvenile eel can be kept temporarily in a medium-sized tank – with perhaps a mated pair of six-line wrasse fish.

Can You Put a Shark in a 55 Gallon Tank?

When it comes to sharks, most species are too large to be kept long-term in a 55-gallon saltwater tank. That said, you can keep juveniles in a reef tank this size to start and then move them to a much larger aquarium once they age. They’ll outgrow a 55-gallon tank quickly so you must be prepared to upsize to at least a 180-gallon version.


To summarize, a 55-gallon reef tank is ideal for a mated pair of medium-sized fish or a small group of schooling fish. When stocking, look for ‘dwarf’ species of saltwater angels, blennies, clowns, chromises, damsels, dottybacks, and wrasses to add vibrancy and movement to your tank. While it’s possible to keep a juvenile eel or shark in a tank this size, it’s not recommended long-term.

I hope this article has provided you with the information you seek regarding how to stock a 55-gallon reef tank. Thanks for reading and happy fish keeping!

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