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Starting a Brackish Tank

Fiddler crabs are an easy beginning species for a brackish tank. Though they're often sold as freshwater pets, they will fare much better in brackish water with some land areas to climb onto as well.

When I wanted to try something other than a freshwater tank, but didn't feel quite yet ready to jump into the world of saltwater, I decided I would try starting a brackish tank. They can be exotic and beautiful; fun and rewarding. I enjoyed learning about different types of brackish fish and their habitats. I would like to share some basic information here about beginning a brackish aquarium.

Brackish tanks are a cross between full freshwater and fully saltwater setups. In nature, brackish habitats have been formed in estuaries, salt marshes, and mangrove swamps, where the rivers and seas intersect and result in a mix of fresh and salt water.

Creating a brackish aquarium is quite simple. It is basically establishing a freshwater tank and adding a little marine salt to it. The three main considerations for me were the species of fish or invertebrates I could choose, how much salt to add, and whether I could use any live plants. (I add many live plants in my freshwater tanks, so while this was something of interest to me, it may not be to some).


A natural brackish water environment will have a specific gravity between that of freshwater (specific gravity of 1.000) and full saltwater (1.021 and 1.025). The specific gravity of brackish water is typically between 1.005 and 1.012. Adding a marine salt mix to your aquarium water can achieve the desired range. (Be sure the salt added is marine salt and not freshwater aquarium salt. Aquarium salt lacks minerals and trace elements that are present in marine salt; fish and invertebrates need these additional elements). A general starting point is to add 1/8 cup of salt per each gallon of water, though the results can fluctuate. Specific gravity can be measured by using a hydrometer or refractometer.

It's also worth noting that the pH of brackish water should remain between 7.8 and 8.4. It's important to test pH on a regular basis, and using a high range pH test kit can help achieve this. Adding some crushed coral gravel or coral sand as substrate will help keep the correct pH and alkalinity. You may want to avoid adding driftwood, or keep driftwood to a minimum, as this generally lowers the pH and will make it more difficult to sustain the proper pH level.


While I personally enjoy the benefits and aesthetics of live plants in my freshwater tanks, I have chosen not to use them (so far) in my brackish tanks. Some hobbyists and experts disagree on whether freshwater plants can thrive long-term in brackish water. Having said that, though, many sources of information testify to the use of certain hardy plants in brackish water. Some of these include java moss, java fern, anubias, and anacharis, just to name a few.

To see the Wikipedia list of brackish aquarium plants, click on the following link: also offers advice on plants in the brackish tank here:

Fake plants and other non-living decor are popular options in place of live plants.


While there are more species available to the freshwater or saltwater aquariums, a number of brackish fish and inverts are widely available commercially. Some of the most common are :

  • Gobies - Knight (also called Fan Dance), Bumblebee, Skunk, or Butterfly Leaf (also called Wasp Fish)
  • Fiddler crabs
  • Mono sebae
  • Mono argentus
  • Puffers - Figure 8, Spotted, Fugu, Ceylon, or Golden
  • Scats- Red, Silver, Green
  • Target fish
  • Colombian shark catfish
  • Archer fish
  • Datnoids
  • Indian Glass Fish
  • American Flagfish
  • Chromides - Green or Orange
  • Shrimp - Amano shrimp, Glass shrimp
  • Olive Nerite snails

Note: Many hobbyists will choose to keep Nerite snails in freshwater, as this will keep them from reproducing. (They may still scatter eggs, though).

Also, if keeping puffers, be sure to include snails in their diet, since they need to file their teeth on the shells. The teeth don't stop growing and this filing is necessary for them.


Many of the available brackish fish grow large and will need larger setups, which is also easier to maintain good water quality. Several of the smaller species (such as fiddler crabs and bumblebee gobies) can be housed in a smaller enclosure. But extra space and higher water volume certainly won't hurt.

Please do your research before purchasing your pets, as we recommend with all animals. All of the different available species will have unique requirements and characteristics.

Also keep in mind that some of these species will be kept in freshwater setups, but will be healthier and happier in brackish water.

Last but not least, as with all aquariums, it is essential that the tank be cycled, have good filtration, and maintained with regular water changes.

Related links of interest:

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