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Brackish Water Aquarium Basics

One of the aquarium topics that seems to create a great deal of confusion amongst our customers is what is a brackish aquarium, and what do you need to successfully keep brackish fish. To shed some light upon this niche of aquarium keeping, I would like to welcome Lexi Jones back to our blog, to share this article about brackish aquarium basics that she has written.
Welcome Lexi!
You might ask, “What is brackish water?”

Brackish water is a mix of freshwater and saltwater, as in estuaries, mangrove swamps, or brackish rivers. The salinity is higher than freshwater, but less than salt water. The specific gravity should be kept between 1.005 and 1.015 for a brackish water aquarium, depending on the type of habitat. You may have to increase the salinity of the water over the fish’s lifespan; this also depends on the type of fish you plan to keep.
Owning a brackish water aquarium is very unique. It is also easier to keep than a saltwater aquarium, being that the fishes in these habitats are used to fluctuations in salinity and water parameters.

The basic supplies you will need to start a brackish water aquarium are as follows:

Aquarium– Brackish aquariums can be set up in just about any size aquarium, I would start with at least a ten gallon size. As with any fish that you plan to keep in an aquarium, you should know the adult size of the fish, and make sure that you have chosen an appropriate match for the size aquarium you have.
Filter– Hang on the back bio-wheel and mechanical power filters, or canister type filters are the best types for a starter brackish water aquarium.
Substrate– sand. This can be any saltwater aragonite sand or even children’s play sand. This sand will help to stabilize the pH of the aquarium, which should be between 7.6 and 8.4 depending on the type of habitat.
Heater– The temperature should be about 80- 82 degrees Fahrenheit. You need to make sure the heater is adequate in size. A rule of thumb is 5 watts of heat per gallon. You will also need a thermometer to make sure the temperature stays constant.
Any tank should have a Glass top or hood. Brackish water aquariums will evaporate water faster than most freshwater aquariums, given the higher temperature recommended. The use of a hood will help to reduce evaporation as much as possible.
Lighting is another requirement, but how much you need varies. If you are only keeping fish, a simple fluorescent bulb fixture will suffice. However, if you plan on keeping plants more intense lighting is required. Also, the light should only be on for around 10 hours a day.
Marine Salt– I use Instant Ocean at home, but any brand of marine salt will work. DO NOT use freshwater aquarium salt; this is not the correct salt to use for brackish or marine tanks.
Hydrometer or Refractometer Hydrometers and refractometers are devices that measure the salinity and/or specific gravity of your aquarium water, and allow you to make sure that you are maintaining the proper salt levels in your brackish aquarium
Water Conditioner– This will remove chlorine and chloramines that are in tap water. Prime and AmQuel are both good water conditioner products to use.
Bacterial Supplement– Products such as Stress Zyme, Stability, or Cycle add beneficial bacteria to the aquarium. The bacteria in these products help to jump-start the aquarium by breaking down organic waste. It may take up to 6 weeks to start a large aquarium. For more information look up Cycling an Aquarium.

That will help you start. If you have any questions feel free to call us, or send us an e-mail

Thanks Lexi
Until next blog,


  1. avatar

    Great post. Very informative. I have always ‘guessed’ on which salts to use for my brackish tank.

  2. avatar

    Interesting account of brackish water. One problem I have always had with a brackish tank is the growth of brown algae and slim. Do you have any suggestion how to avoid this? Even with the right amount of light because there isn’t any plants—generally—the algae seems to grow. Thanks!

  3. avatar

    With any aquarium, the key to controlling algae is managing the nutrient levels, this is true for Brackish aquariums also. Maintaining water that is low in nitrate and phosphate free is the best way to prevent algae problems. You may need to use a filter on your water source, depending upon its quality. A reverse osmosis system will produce the best quality. And using phosphate removing filter media will control sources of phosphate from food and fish waste.
    This is especially true in brackish systems because, as you pointed out, you are really limited in natural methods for removing these nutrients by means of live plants and algae eating invertibrates that will survive in an aquarium.


  4. avatar

    Setting up new brackish tank and want to keep high salinty puffer fish, etc. 2 questions ?? can i use Black onyx subtrate good for fresh and salt water?? and when filling tank for first time and during water changes, how do i get the salt mixed water from bucket to tank without mess?? i used freshwater gravel vac before so can i use this in same way ??

  5. avatar

    Black onyx should be fine, it may not buffer the hardness/pH as well as crushed coral or cichlid gravel. A gravle vac or small pump or powerhead can help you to transfer the water without having to lift the mixing vessel.

  6. avatar

    I have done some research into brackish water tanks / Fish, I am about to start the cycle on a new tank,The one bit of information that has gone with out an answer is, what if any bottom feeders that can go into a brackish tank are out there,are there any snails shrimp or crabs that can be kept in a brackish water tank. I have not committed to the fish that will be housed. I was thinking of of puffers & gobys, but I am not sure. Any house cleaners for the brackish tank? Help….

  7. avatar

    Im also having a hard time controlling the brown algae in my brackish tank… I’m curious if this algae is harmful to my fish? African Cichlids?? Thank you

  8. avatar

    Not harmful, just unsightly. Maintenance, regular testing and water changes can help to keep in under control. It usually gets really bad if there are too many nutrients in the tank, so be sure to keep up with a regular maintenance schedule and avoid overfeeding.

  9. avatar

    Hello everyone, I found out a couple of things since my last posting.First, fiddler crabs are really brackish water crabs and will eat any and everything from the substrate. They make great bottom cleaners. “Note” if you are going to try fiddler crabs a few things to know, they will climb out of the tank, they are amphibian.I provided a shelf thats used for coral frags,they are magnetic so they are easy to place near my plastic plants at the top just above the water line. The crabs climb up the plant and on to the shelf. If you want to try this make sure you get a good size crab other wise it’s just fish bait. As for the brown algae, I had a small break out growth, I thought it was beause of all of the nitrite due to the cycle process. I removed the items with the growth into a bucket,I used a half tea spoon of bleach in the water,i let the items sit for one day. I did a 15% water change,rinsed the bleached items with bottled water treated with stress zyme. I used poland spring with instant ocean to replace the water, I used 2 table spoons of salt per gallon.
    No more brown algae since then, it did not stop the cycle process either. May not be the pros way but my tank is crystal clear, One fan dancer goby,one green scat,and two silver sharks/columbian sharks.(catfish). I am learning, albiet slowly, all advise from knowledgable aquirst is welcome. Thanksto everyone for sharing your knowledge.

  10. avatar

    I have been thinking about getting a fish, I find watching they swim around to be relaxing. I better find what size aquarium I will need, so I don’t get one too big. Plus it would need to be heated also.

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