Brackish aquarium is an aquarium with salty water. The water is called “brackish” because of its salinity or salt level. It is the middle ground where freshwater and marine water mix.

Keep reading this article to find out more about brackish aquariums and how you can set up one.

What Does Brackish Water Mean?

Brackish water is the water found at the point where fresh water and saltwater meets. The brackish water is the middle ground between freshwater and marine water. This point is called estuaries; it could be mangrove swamps or salt marshes, and the water found in these areas is called brackish.

The Brackish water is home to different species such as scats, archers, some livebearers, gobies, black molly, Sailfin molly, Cichlids, Pufferfish, catfish, etc.

With the understanding of brackish water, brackish aquariums are unique aquariums with salty water instead of regular freshwater aquariums. Brackish aquariums are top-rated among hobbyists as it’s one of their areas of specialization. Keep reading to discover how you can set up one maintenance and suitable fish suitable for the brackish aquariums.

How to Make Brackish Water?

The brackish water salinity level differs depending on the type of brackish aquarium you want to set up. Generally, hobbyist maintains a level of 1.005 to 1.010 depending on the type of fish, but the salinity level can fluctuate.

Creating brackish water is not tasking with you bearing in mind the water parameters to make it conducive for the inhabitants.

How to Set Up A Brackish Tank

Setting up the brackish tank is different from the freshwater tank but with a bit of extra.

The following equipment is needed when setting up a brackish fish tank.

1. Tank

Tank’s choice depends basically on the type of setup and the quantity of fish contained in it. Sizes vary from as small as 5.5 gallons to as large as 55 gallons or more. Different types of setup later in the article will better help you with the choice of tank.

2. Heater

There are different heaters used for aquariums but be sure to get quality heaters that will not shatter. Submersible heaters are great at dispersing heat around the tank and are durable.

It is recommended that you get a heater produced for freshwater and saltwater use and appropriate size. Generally, hobbyist sets heaters at 5 watts of heat per gallon.

3. Substrate

The substrate of a brackish water tank varies from sand to gravel. Aquarists many times use marine aragonite sand or crushed coral. Depending on your preference, if you want live plants in your tank, then a 1-inch layer of substrate is needed. A fish-only brackish aquarium requires a thin layer of substrate as more significant layers tend to build up anaerobic spots.

4. Filter

The most suitable filters for a brackish water tank are canister filters or bio-wheel filters. Sand substrate is used for the brackish tank; therefore, an under-gravel filter will not be appropriate for use. 2 filters are required for a bigger tank than 20 gallons, placed on opposite sides of the aquarium. Water circulation around the tank is about ten times per hour; therefore, two 150gph or one 300gph filters are needed for a 30-gallon aquarium.

5. Cover

A glass top cover is needed to cover the tank. You don’t leave the tank uncovered. Unlike freshwater, the level of evaporation of the brackish water is higher, so the tank should be covered to prevent evaporation.

6. Plants

Plants are optional in a brackish tank as they eventually die off or are eaten up. Java Moss and Java Fern plants are plants that may likely survive in a brackish water tank. Artificial plants can be used for decorating the tank to mimic the natural habitat best.

7. Light

The plants in the tank determine the watts of light in the tank. Therefore, 1.5 watts of light is recommended per gallon of water. This lighting will serve as the natural sunlight in the natural environment.

8. Thermometer

The thermometer is needed to check the temperature of the water. It is imperative to make sure that the brackish water is at the right temperature.

9. Hydrometer

A swing handle hydrometer is excellent for the brackish water tank. It would help if you had the hydrometer to measure the salinity of the water. The hydrometer is significant equipment for a brackish water tank.

10. Water Conditioner

The aquarist ensures that the water to be placed in the tank is well treated before use. Chloramine and chlorine are extracted from tap water before use.

11. Marine Salt

Any brand of marine salt is okay for your brackish water aquarium. However, ensure you get suitable marine salt for brackish water tanks and not freshwater tank salt.

All of the above-listed equipment is needed for setting up a brackish tank.

As mentioned above, brackish water is found in different areas like the estuary, mangrove swamps, and rivers. As the brackish water area differs, so is the fish. Some fish are found in the ends of fast-flowing rivers, some in the mangrove swamps and slow-flowing estuaries.

Below are three different categories of recommended setups of the brackish water aquarium.

1. Estuary Brackish Water Aquarium

– Tank

A massive tank of about 125 gallons is best appropriate for setting up an estuary brackish water aquarium. The water movement in the estuaries area is a slow, moderate flow; therefore, aquarists ensure the aeration from filters is adequate.

– Fish

There are different fish that can be in your estuary brackish water aquariums. You can pick from either 6 Monos, 6 Sebae Monos, 5 Colombian Shark Catfish, or 5 Scats.

– Plants

Plants are not likely to survive after specific gravity is raised over 1.015. For that reason, aquarists replace plants with marine algae such as Caulerpa green algae after plants are eaten up or die off.

– Water Temperature

Water temperature in an estuary brackish water tank is between 80 and 82 F.

– Water pH

Water pH of brackish water in an estuary tank is between 7.5 and 8.5.

– Driftwood/Rocks

You can sparsely decorate the tank with crafted branchy driftwood and rocks. Please ensure the wood is treated to prevent them from leaking.

– Salt Level

As the fish in the estuary grow older, they move to the ocean, where the salt level is higher. So, to simulate the same natural environment in your tank, the salt level is increased with time. 2 tablespoons of marine salt per gallon of water is needed for setup.

An additional tablespoon per gallon of water is required every six months after water in the tank is replaced. Ensure to check your hydrometer regularly for the measurement of salt in the water. No more salt is required after the hydrometer is reading between 1.020 and 1.025.

2. Fast-Flowing End of River Brackish Water Aquarium

Brackish water is not found only in the estuaries, as people generally believe. There is brackish water just before the end of the outward flowing rivers that go into the estuaries.

Since water found in this area is fast-flowing, water movement in the aquarium should mimic the same. As opposed to the Estuary aquarium, increased aeration and movement are needed in the river brackish water Aquarium. Different fish can be in this tank, such as Gobies, Mollies, Puffers, Bumble Bee gobies, and Silversides.

– Tank

Tanks for this setup vary based on the choice of fish that will be in the tank. Below are the sizes of tanks and the suitable amount and type of fish that should be in them.

  • 5.5-gallon+ tank will accommodate 3 Bumble Bee Gobies
  • 10-gallon+ tank will accommodate either 3 Mollies and 1 Knight Goby or 3 Mollies and 3 Bumble Bee Gobies. You can also have either 3 Glassfish and 1 Knight Goby or 3 Glassfish and 3 Bumble Bee Gobies.
  • 30-gallon+ tank will accommodate 3 Mollies, 6 Celebes Rainbows, 7 Bumble Bee Gobies or 3 Glassfish, 6 Celebes Rainbows, and 7 Bumble Bee Gobies. It can also contain 3 Mollies, 4 Glassfish, 2 Knight Gobies, 3 Bumble Bee Gobies or 2 Green spotted Puffers, and 5 Bumble Bee Gobies. One can also have 2 Figure Eight Puffers and 5 Bumble Bee Gobies or 2 Orange chromides and 2 Knight Gobies.
  • 55-gallon+ tank can contain 3 Mollies, 3 Glassfish, 2 Celebes Rainbowfish, 2 Knight Gobies, and 5 Bumble Bee Gobies. The tank’s exact size can contain 3 Green Spotted Puffers and 7 Bumble Bee Gobies or 3 Figure Eight Puffers and 7 Bumble Bee Gobies. In addition, you can have 3 Orange Chromides, 3 Knight Gobies, 6 Bumble Bee Gobies or 3 Ceylon Puffer, 3 Mollies, and 5 Bumble Bee Gobies.
  • 125-gallon+ tank will accommodate 3 Siamese Tiger Fish or 3 Mollies, 5 Glassfish, 10 Celebes Rainbow Fish, 4 Knight Gobies, and 8 Bumble Bee Gobies. You can also Put 8 Green Spotted Puffers and 10 Bumble Bee Gobies or 8 Figure Eight Puffers and 10 Bumble Bee Gobies. It can also contain 6 Orange Chromides, 4 Knight Gobies, and 8 Bumble Bee Gobies or 3 Target Fish.

All of the above-listed tanks and fish is all about choice; you can choose between small, medium or large tank. Nevertheless, your tank choice must be suitable for the fish you want to place in the tank.

As shown above, fish combinations can also differ as some fish can stay together while some can’t. For example, Target Fish can stay alone in a tank or keep another large brackish water fish that can defend themselves.

– Plants

Java Fern, Hair Grass, Anubias, and Vallisneria are adequate for the water’s fast movement in the tank. Artificial plants can also be used for decoration as live plants die eventually.

– Water Temperature

Water temperature in a fast-flowing river brackish water tank is between 80 and 84 F.

– Water pH

Water pH of brackish water in a fast-flowing river tank is between 7.5 and 8.5.

– Driftwood/Rocks

Tall driftwood should place in the background of the tank with short ones on both sides. One or two rock caves should be placed in the tank for shelter, with Java fern and Anubias placed by the caves.

– Salt Level

The specific gravity of 1.005-1.010 is suitable for most of the fish listed above except the Green Spotted Puffers. Green Spotted Puffers prefer a higher salt level with a specific gravity of about 1.010-1.020.

3. Mangrove Swamp Brackish Aquarium

The water movement in the mangrove swamp is slow, with mangrove roots and plants covering the surface. The setup of this tank is like a Paludarium with half land, half water. A Canister filter with long tubes is suitable for this setup.

– Tank

A 55-gallon tank is needed for this setup for the fish to have a sufficient swimming area.

– Fish

2 Archer Fish or 3 Mudskippers and 3 Fiddler Crabs are suitable in a 55-gallon+ tank. 125-gallon+ tank will contain 4 Anableps or 4 Archerfish or 6 Mudskippers and 6 Fiddler Crabs.

– Plants

Mangroves can be planted on the land part just by the side of the water. Artificial aquatic plants can be in the water part for decoration, but you can also try out the Hairgrass, Vallisneria, and Java Moss.

– Water Temperature

Water temperature in a Mangrove swamp brackish water tank is between 82 and 86 F.

– Water pH

Water pH of brackish water in a Mangrove swamp tank is between 7.5 and 8.5.

– Driftwood/Rocks

Crafted tree root driftwood is excellent for this setup. Additionally, Java moss and artificial plants can be used as floating plants to cover the water’s surface for perfect simulation.

– Salt Level

The specific gravity of 1.010-1.015 or 3 tablespoons of marine salt per gallon of water is adequate for the fish found in the Mangrove swamp area. A partially subdued light is needed in the tank to make your mangrove swamp tank look more realistic.

Maintaining a Brackish Water Fish Tank

Like any other fish tank, the brackish water tank needs to be cared for too.

Below are some ways to maintain the brackish tank

  1. 15% of water in the tank should be clean once a week.
  2. Add the exact dosage of salt as before except for estuary water which salt increases every six months.
  3. Use the back end of the fishnet to stir up the sand in the tank once or twice a week.
  4. Scoop out debris stirred up with the net.
  5. Feed the fish in the tank twice daily.
  6. Water temperature should not be below 80 F as it helps increase fish metabolism.
  7. Include vegetables in the diet of fish like knight Gobies, Mollies, Scats, and Monos.
  8. Puffers require an occasional meal of snails as it helps to reduce the size of their beak.


  • The brackish water aquarium is unique compare to a regular freshwater Aquarium.
  • The brackish water Aquarium is a saltwater Aquarium.
  • Different fish are found in different brackish water tank setups.
  • The size of the tank depends on the fish to be placed in the tank. The tank can be as small as 5.5-gallon+ and as large as 125-gallon+.
  • The water temperature of brackish water should not be below 80 F.
  • Brackish water salinity level varies among setups and must be near accurate to prevent shock.
  • Stirring the water in the tank once or twice helps prevent anaerobic spots release deadly gases into the tank.
  • Use quality equipment for your brackish water tank setup for durability.

Setting up a brackish water tank is worth the money and the effort. Right in your home is the best of nature’s remarkable and unique species.

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