How to Set up (and Maintain) A Brackish Aquarium


How to Set Up (and Maintain) a Brackish Aquarium

You may feel that you have tried all aspects of freshwater aquarium keeping for some time. Consider setting up your first brackish fish tank that will allow you to try an entirely new category of animals. Many aquarists get a little nervous about making brackish water, but in our opinion, it is quite easy for anyone who has kept freshwater tanks before. This step-by-step guide will show you how to make and maintain your first brackish tank.

The Pros and Cons of Brackish Water Tanks

Before jumping into this new endeavor, let’s weigh the costs and see if a brackish aquarium is right for you. Brackish aquariums offer the opportunity to:

Keep new species of aquatic animals

, including:

– Green spotted puffer, (Dichotomyctere.nigroviridis); – Figure 8. puffer (Dichotomyctere.ocellatus/Tetraodon biocellatus); – Bumblebee flyby (Brachygobius.spp.). – Knight goby, Stigmatogobius sadanundio – Mudskipper, Periophthalmus species spp. – Banded archerfish (Toxotes jaculatrix) – Red claw crab (Perisesarma bidens)

Atlantic or West African mudskipper (Periophthalmus barbarous)

You could also try breeding nerite snails and amano shrimp, which can only survive in brackish waters. Plus, certain freshwater fish like guppies and mollies can do well in brackish water.

Brackish water is a great choice for certain species of livebearers because it contains all the necessary trace minerals and water parameters to maintain their optimal health. Brackish water can also kill many parasites and freshwater diseases. Therefore, fish farms often breed livebearers in part fresh and part salt water to raise healthier stock and save costs.

Also, put your mind at ease because brackish aquariums do not require a precise amount of salt. Brackish species, unlike corals in saltwater reef aquariums, can withstand fluctuating water conditions. They live in estuaries that are where rivers and streams meet with the ocean. Depending on the tides or rainfall, they can experience full fresh water or full salt water all within the same day. Your fish will be fine as long as they have the bare minimum amount of salt (see below for more details).

Estuary California, where fresh water is mixed with salt water

Conversely, brackish tanks do limit you on the types of animals and plants you can keep. Moreover, these species are sometimes hard to find since most fish stores don’t specialize in brackish water. Tank maintenance does require some additional steps for adding the right amount of salt and measuring the specific gravity (SG) of the water. Salt creep, or salt residue, can form in areas where water is sprayed out of tanks. You can wipe it off with a damp cloth, or place craft mesh on the tank lid holes to reduce it.

Materials List for a Brackish Aquarium

The supplies you need for a brackish tank are almost exactly the same as a freshwater tank – such as a fish tank, aquarium stand (optional), lid, light, heater, thermometer, filter, dechlorinator, and aquarium siphon. For substrate, you have the option of using regular gravel, normal sand, or any other inert product. If you have low pH water, we recommend using aragonite and crushed coral to buffer the water and create a semi-marine environment.

The salt must be marine or reef salt and not regular aquarium salt. Aquarium salt is made from sodium chloride, but marine salt contains sodium and other essential minerals such as magnesium, potassium, calcium. In order to monitor the amount of salt in the water, we suggest purchasing a refractometer to measure specific gravity (SG). They are slightly more costly than a hydrometer but they are easier to use and more accurate.

Refractometer is used to determine the specific gravity and amount of salt in water

What plants can survive in brackish water? We have seen many lists on the internet of plants that are safe for brackish water, but we found that most plants suffer when salt is added. The mangrove tree is the only surefire plant we know of that handles everything from full fresh to full salt water. To make our own tanks, we purchase mangrove seedlings via online sites. We then attach them to our aquariums with heavy duty wire. We have a dedicated light source that shines on the mangrove so it can grow more leaves. In brackish aquariums, you may need to occasionally wipe off any salt spray on the leaves to make sure it can still photosynthesize. Once the mangrove is tall enough, you can plant it in an aquarium with deeper substrate and add root tabs to feed it.

The other plant we have had success with is java fern. The plant had to be slowly adjusted from freshwater into low end brackish (SG of 1.055) over the next two to three months. While the plant has not died, it does not grow very quickly either. The other commonly available “brackish” plants, like anubias and hornwort, only seem to handle extremely low salinity levels that would not be acceptable for most brackish animals. See this forum post for more details on other hobbyists’ experience with brackish water plants.

Java fern (Microsorum pteropus)

How to Set Up a Brackish Aquarium

Again, most of the instructions are very similar to installing a freshwater aquarium, so we will focus our attention on how to prepare the water. It is important to achieve a

Specific gravity between 1.004 – 1.012

. Our brackish tanks are kept at 1.005 to 1.008.

1. Find a location for the fish tank and assemble the aquarium stand if needed. 2. Use fresh water to rinse the tank and accessories. If using aragonite or crushed coral, make sure to rinse the substrate multiple times to minimize cloudy water issues. 3. Place the aquarium on the stand and add the substrate, equipment, and decorations. 4. You can fill the aquarium with dechlorinated waters. 1. If you plan on slowly acclimating your fish and plants from fresh water to brackish water, then just add normal drinking water as usual without any salt. 2. For brackish water, fill the tank to 80% with fresh water. Then add 2 tablespoons (Tbsps) of reef salt per gallon. Allow the salt to dissolve in the filter or powerhead circulation. After about 8 hours, check the specific gravity. Depending on what the refractometer reads, you can add fresh water or marine salt to the tank until the desired SG has been reached.

If this is a brand-new setup, you need to cycle your aquarium before adding any fish to ensure that the fish tank’s ecosystem can safely process the toxic ammonia produce by your fish’s waste. You can cycle a freshwater tank or a brackish one the same way. However, brackish water is more difficult for plants to use. Please see our article about aquarium cycling.

Knight goby (Stigmatogobius sadanundio)

How to Acclimate New Fish for a Brackish Tank

Most brackish fish that are sold at fish stores are usually kept in freshwater environments. If you are purchasing brackish fish, it is necessary to slowly adapt their bodies to the saltwater environment over a period of at least four weeks. If you are setting up a new aquarium, use Step 4a from the above instructions to make a fully freshwater tank. Once it is cycled, add the fish and slowly add marine salt over the course of four weeks until you achieve the required SG.

If you already have an established brackish aquarium with fish and you want to add new animals that are accustomed to fresh water, set up a separate quarantine tank or tub that is fully fresh water. You can then use the same process as before to gradually increase the SG until your tank is the right size. Because the animals are in a quarantine system where salt is being added, some parasites and diseases may be eliminated in the process, which is a nice side benefit.

Banded archerfish (Toxotes jaculatrix)

How to Change Water and Maintain a Brackish Water Tank

When it comes to tank maintenance, the steps are exactly the same except for the water preparation. You must track the amount of water removed from the tank to maintain the same salt content. For example, let’s say you decide to do a 50% water change on a 20-gallon aquarium.

Based on our

Start concentration of 2 Tbsp Salt per Gallon

, that means you will need to add back in 10 gallons of dechlorinated water and 20 tablespoons (or 1 1/4 cup) of salt. Manufacturers of reef salt recommend premixing the water with salt in a container or bucket. You can fill two 5-gallon buckets of 5 gallons with 10 tbsp each salt. You can mix large quantities of water with a powerhead or stir the salt by hand. Marine salt is very fast to dissolve. Pour the brackish water into the aquarium and then measure the tank’s SG after a few hours have passed. Salt can be added to the tank to increase its SG. You can also remove any tank water from the aquarium and replace it with dechlorinated fresh water to lower the SG.

Remember that brackish fish can live in a wide range of salinity, so do not worry too much about adding salt directly into the tank if needed. For faster distribution, we like to add salt around the power head or filter output. Also, if the water in the aquarium is too low and you need to top off (or replace) the evaporated water, add fresh water only. Salt doesn’t evaporate so don’t add brackish water to your aquarium or the SG will rise.

How frequently should you test for salt? After every water change, we test the SG within a few hours to the next day.

Bumblebee goby (Brachygobius doriae)

Brackish water tanks are a great way to have fun, especially when you think about all the species you can keep. They are much easier than saltwater reef tanks, and if you are confident with keeping freshwater aquariums, you will be successful with brackish ones. If you have any more questions, please visit our forum and many experienced brackish fishkeepers will be happy to help you.