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How many fish in a 55 gallon saltwater tank? 2021

how many fish in a 55 gallon saltwater tank
How many fish in a 55 gallon saltwater tank

  • A 55-gallon tank provides far more options when compared to smaller tanks, such as 5 gallon tanks and 10 gallon fish tanks.
  • Large tanks like this are easier to maintain since the more water you have, the harder it is for pollutants to build up. They take longer to clean though – so you will need to set extra time aside for wiping the larger glass walls and performing bigger water changes.
  • This is not difficult however, even beginners will be able to maintain a healthy tank if they pick some hardy fish.
  • As you might have thought, big tanks cost more. Expect to pay $200 or more for a new 55 gallon one. This number will be more if you have to buy your equipment separately.
  • This size of tanks will weigh more too. Once filled with just water, it will weigh around 600lb. The weight will increase even more once you add the decorations and fish.

55 gallon saltwater tank specifications:

55 gallon saltwater tank size:  A 55-gallon tank is one of the more popular sizes when it comes to aquariums, as it allows for a lot of swimming space. Its size serves as an excellent display tank and is readily available at most pet shops. The 55 gallon fish tank has the standard dimensions of 48 x 13 x 21.

55-gallon saltwater tank weight: To calculate the weight of the tank, you should pair in mind the weight of the glass, the weight of the tank with gravel and plants, sand, rocks, lighting, and filtration. you should consider what kind of water you want to fill the tank with, freshwater or saltwater this will make a slight difference. The density of salt water causes it to be slightly heavier than freshwater but not by much.

So let us see the weight of the essential items.

Acrylic Aquarium


Glass Aquarium


Weight of Water

Freshwater = 456.5

Saltwater = 467.5

  • If you want to add gravel the recommended amount for a 55 gallon aquarium is 40 lbs, and if you want to add plants it will not make a difference as they are light. Most saltwater tanks use a substrate of sand or crushed coral. This will add to the overall weight. so the recommended weight for a 55 gallon aquarium
    is about
    55-110 pounds of sand.
  • As rocks are an important factor for your saltwater tank most saltwater tanks use a substrate of sand or crushed coral. This will add to the overall weight. so the recommended weight depending on the space you have in the tank. According to lightning filtration and other equipment, the weight depends on the type of each component.

The best fish for a 55 gallon saltwater tank:

When choosing the best saltwater fish for a 55-gallon tank, it’s important to not only look at their size but their behavior patterns and tank mates as well. the 55-gallon tank is a great choice for many hobbyists and you will have plenty of fish options to choose from such as :

Coral Beauty Angelfish: 

Coral Beauty Angelfish
Coral Beauty Angelfish
  • Because of its attractive colors (bright orange, yellow, and red body and brilliant blue fins), this fish is a good choice for a beautiful saltwater tank. Only growing to about four inches in length, which makes one of the best saltwater fish for a 55-gallon tank. It comes from the Great Barrier Reef of Australia, it is considered to be easy to care for and is also quite hardy.
  • This kind of saltwater fish is omnivorous and enjoy a variety of food, including spirulina, shrimp, marine algae, and other angelfish flake or pellet is small. These fish tends to be aggressive amongst each other but as long as they are fed well they will get along with other aquarium inhabitants, including invertebrates and corals.

Blue/Green Chromis:

Blue/Green Chromis
Blue-Green Chromis
  • This kind is tiny, bright fish add color and beauty to any aquarium. With their iridescent, pale blue and green colors, these fish stand out, even in larger aquariums. They are also easy to care for and can live for up to 15 years. In a 55-gallon fish tank, you can keep from 3 to 7 of this kind together.
  • These fish are known to be quite peaceful and get along well not only with their own species but also with other fish and other aquarium inhabitants. They also tend to ignore corals, which makes them a good choice for reef aquariums.

Royal Gramma Basslet:

Royal Gramma Basslet
Royal Gramma Basslet
  • It is a colorful fish mostly yellow and purple. Only grows to about three inches long. It is a small fish which makes it a good choice for small tanks besides it is recommended for beginners.
  • It is a peaceful fish with other tank mates, but they tend to fight each other unless they are a mated pair.
  • They prefer to have plenty of rocks in the tank and provide caves for them to hide in.
  • They eat crustaceans, zooplankton, the typical brine shrimp, and Mysis shrimp. Royal gramma basslets are slow swimmers and prefer to have plenty of hiding places. They are somewhat aggressive towards members of their own kind, but in a 55-gallon aquarium, there is enough space to keep a pair.
  • You can find it in local fish stores or online.

Flame Angelfish: 

Flame Angelfish
Flame Angelfish
  • It is an amazing fish with bright red and orange bodies, bold black vertical stripes, and deep blue tips on the dorsal and anal fins. It is a good option for intermediate aquarium keepers.
  • They are omnivorous and feed on shrimp, marine algae, spirulina, and other angelfish cake and pellet foods.
  • Flame angelfish can be aggressive towards each other. However, they adapt well to living in aquariums and only need a small amount of space, making a 55-gallon tank a good choice.

Purple Firefish: 

Purple Firefish
Purple Firefish
  • also known as Dartfish it is a small fish long, narrow fish that grow to between three and a half and four inches long with a lot of different colors and it is recommended for small tanks. They are very peaceful fish and shouldn’t bother other tank mates.
  • They are carnivores and prefer a mixed diet of seafood, frozen foods, vitamin-enriched brine shrimp, and Mysis shrimp. In order to maintain their vibrant colors, they require this diet or the colors will fade.
  • If you decide that the purple firefish is the best choice for you then make sure you have a tight-fitting lid or canopy on your tank.
  • Only a small amount of space is required for the purple firefish to thrive, so a 55-gallon tank with plenty of live rock and hiding places is an ideal setup. These fish are also reef compatible. They have known jumpers and do a great job of finding the smallest space to jump out of.


Bluestreak cleaner wrasse: 

Bluestreak cleaner wrasse
Bluestreak cleaner wrasse
  • These small fish Grow to about five and a half inches. It is known to be a peaceful, active additions to the home aquarium.
  • They can also be kept in a reef aquarium. It is a good choice for experienced keepers. It can thrive in an aquarium as small as 30 gallons.
  • However, a 55-gallon tank is even better. the Bluestreak cleaner wrasse will clean the parasites from other fish, which is where its name comes from. 



is one of the most common fish in saltwater tanks, as there are 28 kinds of it. Besides their beautiful color, These fish are active in the tank and you will love watching them moving inside the tank. The recommended number of these fish to be in a 10 gallon saltwater tank is just one. If you plan on having a pair you should consider a larger tank of 20 gallons or more.


 the most popular types of clownfish:

Common fish:

  • also known as the False Percula Like all kinds of clownfish, the female is larger and can reach up to 4 inches but according to the male reaches 3 inches.
  • Found in shallow reefs in the Eastern Indian and Western Pacific Oceans, the Common Clownfish has a distinctive wobbling style of swimming that makes them a darling of the pet world.

true Percula:

  • It is the smallest kind of clownfish, it’s also known as orange percula .
  • It can be found in a relatively small range in nature, around New Guinea and Northeastern Australia. Their rowing pectoral fin motions are adorable and give them a lovely appearance as they swim.
  • True percula clownfish are sensitive to low water quality compared to other kinds of clownfish.
  • Water changes should be regular and testing is done frequently to keep them in optimal health. If ammonia and nitrites are allowed to spike, their immune systems will suffer, opening them to infections from Clownfish Disease (Brooklynellosis) and Marine Ich.

Cinnamon clownfish:

  • also known as the fire clownfish, these fish are one of the largest kinds of clownfish. its size could be 5 inches.
  • When they are kept in a small aquarium they tend to claim the whole tank as their territory, causing problems for other residents in the tank.
  • Cinnamon Clownfish are aggressive towards other Clownfish and should not be kept with other types. a pair or single individual is best.

tomato clownfish:

  • Also is one of the largest kinds of clownfish.
  • It is a rough kind of clownfish that you should give it a lot of attention to.
  • They are found in the Western Pacific Ocean from Japan down to Indonesia. 
  • It is a recommended type of clownfish as it is sort of cheap and suitable for a semi-aggressive environment tank. there are different kinds of fish that could be kept with a full-grown tomato fish such as Triggerfish, Tangs, Damselfish, and Angelfish.
  • As large, eager eaters, they tend to intimidate shy tankmates. Like all types of Clownfish, they happily accept a mixture of flakes and meaty live and frozen items such as Brine Shrimp and chopped clams.

maroon clownfish:

  • These are the largest type of clownfish, with females reaching up to 7 inches.
  • They are found in the Western Pacific Ocean, from Indonesia down to Northern Australia. these kinds tend to be aggressive when they get mature even among each other. Sometimes females kill male fish just because they are in a bad mood.
  • They are a clever kind who can differentiate the guest from their owner.
  • Although they are large and aggressive they also look adorable besides easy to care for. pair in mind this kind can be kept in a tank at least 55 gallons.

clarkii clownfish:

  • They are one of the widespread kinds of clownfish both in aquariums and nature, Found throughout the Indian and Western Pacific Oceans.
  • They are non-aggressive kinds that give space to their mates in the tank but they could be aggressive in small tanks.
  • Inexpensive, hardy, and an excellent first Clownfish for the saltwater aquarist with a medium-sized tank.

How many fish can you put in a 55 gallon saltwater tank?

  •  A rule of thumb for determining the maximum number of fish to keep in any size tank is one inch of fish per one gallon of water.
  • But this doesn’t mean that you should exceed 55 inches of fish in a 55-gallon tank. add only 10 inches of fish and wait a month.
  • Doing this creates the nitrogen cycle, a process that establishes helpful bacteria in the water and removes ammonia, which, in abundance, will kill your fish.
  • Test the levels of ammonia and nitrite daily; once they return to zero, which means they are balancing themselves out, you can add more fish. A 55-gallon aquarium would house only about 12 inches of fish, so to be safe, limit it to hold three (4-inch) fish or two (6-inch) long fish.

How to clean a 55 gallon saltwater tank?

There are three goals for cleaning up your fish tanks:

  • Regulate the nitrogen cycle: in this process, ammonia is converted by bacteria to nitrite and then to nitrate and both of them (ammonia and nitrate) are toxic to it’s important to have bacteria as it converts harmful compounds to nitrate therefore we can remove the nitrates which are less harmful to fish by changing the water.
  • Remove dissolved organic compounds: organic compounds consist of carbon and hydrogen. There are two types of organic, first, one is dissolved organic which is any organic material that can pass through 0.2 0 1.0 um filters and the second one is particulate organic (food waste) which will not pass through your filter. If you have plants in your tank it will use some organics and the rest can be removed by regular water changes. 
  • Refill the essential minerals: after cleaning the tank you should use a product to add these essential minerals into the aquarium.

 the steps you should make to clean your tank.

  • Prepare all the supplies you need while cleaning (A siphon gravel vacuum – Algae scraper/pad – Used clean towel – Water testing kit – Powerhead and heater – A salinity probe)
  • Use a siphon gravel vacuum, with an attached hose to clean the gravel and remove the water. You should suck up small amounts of gravel using the siphon, the waste will then be sucked through the tube into the bucket along with some of the water, and the gravel will fall back into place.
  • Use the magnetic algae cleaner to clean the glass of the tank
  • Clean up the tank filter. This step depends on the filter type. The most common type of filter is a sponge filter. To clean this, you should remove it and rinse it out in the bucket of water that you have removed from the tank. Never put your filter under tap water, because it removes the beneficial bacteria which is necessary for your tank. If your filter contains carbon, ammonia absorbers, or, ion-exchange resins it will need replacing every couple of weeks because it will no longer be able to absorb materials. You should also clean the rest of the filter, including the tubing; use a filter brush for this.
  • Refill the tank with saltwater but you should consider the salinity and the temperature of the water. Check the water again after a couple of hours and also check that the water is not cloudy.

Q & A about fish in a 55-gallon tank

How often should I clean my fish tank?

For a saltwater tank, you should change 10% of the water every week for the first year of keeping the aquarium.

The more fish you have, the faster the water needs changing.

During the first few months of keeping fish, you should watch the water conditions of the tank regularly.

Also will come to your mind great ideas on how often your tank should be cleaned.

The parameters depend entirely on the species which you are keeping.

How many clownfish can I put in a 55 gallon tank?

The recommended number of clownfish in a tank is two, regardless of its dimensions. Why do we exactly recommend this number? simply this is because of the kind of fish we are talking about. Clownfish are aggressive so if you put more than this number that may end up with an aggressive behavior originating from the mating pair. On the contrary, keeping a single clownfish may result in a weary, depressed fish.


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