How to Set up (and Maintain) A Brackish Aquarium

How to Set Up (and Maintain) a Brackish Aquarium

If you’ve been keeping freshwater aquariums for some time, it may seem like you’ve tried every aspect of the hobby such as aquascaping and African cichlids. Consider setting up your first brackish fish tank that will allow you to try an entirely new category of animals. While many aquarists feel nervous about making brackish waters, it’s actually quite simple for anyone who has ever kept freshwater tanks. This step-by–step guide will help you create and maintain your brackish aquarium.


The Pros and Cons of Brackish Water Tanks

Before you jump in to this new venture, we need to weigh the benefits and decide if a brackish tank is right for us. Brackish has the advantage of being able to

keep new kinds of aquatic species

, including:

– Green spotted puffer (Dichotomyctere nigroviridis) – Figure 8 puffer (Dichotomyctere ocellatus or Tetraodon biocellatus) – Bumblebee goby (Brachygobius spp.) – Knight goby. (Stigmatogobius Sadanundio). – Mudskipper. (Periophthalmus.spp.). – Banded archerfish (Toxotes jaculatrix) – Red claw crab (Perisesarma bidens)

Periophthalmus Barbarous (Atlantic or West African mudskipper)

It is possible to breed nerite and amano snails. Their offspring will only survive in brackish. Plus, certain freshwater fish like guppies and mollies can do well in brackish water.

One of the advantages of putting certain livebearers in a brackish tank is that brackish water contains all the trace minerals and water parameters necessary for maintaining optimal health in these species. 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. Unlike the corals in saltwater reef tanks, brackish species are used to fluctuating conditions because they live in estuaries where rivers and streams meet the ocean. They can have full freshwater or full salt water depending on whether it is raining or not. Your fish will be fine as long as they have the bare minimum amount of salt (see below for more details).

Estuary California where freshwater mixes 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. There are additional steps that must be taken to maintain a tank, such as adding the proper amount of salt or measuring the specific gravity (SG). Finally, salt creep or leftover salt residue can occur in areas where water splashes out of the tank, but you can easily wipe it off with a damp cloth or install some craft mesh over the tank lid holes to mitigate 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. You can choose from regular gravel, sand or other inert materials for your substrate. However, if you have soft water with low pH, we highly recommend getting aragonite or crushed coral to help buffer the water and replicate a semi-marine environment.

For the salt, you must buy marine or reef salt meant for saltwater aquariums, not regular aquarium salt used for freshwater aquariums. Aquarium salt is made of sodium chloride (NaCl), but marine salt contains sodium chloride and many other essential minerals, like magnesium, potassium, and calcium. To measure the specific gravity of the water, a refractometer (SG) is recommended. Yes, they are slightly more expensive than a hydrometer, but we find them to be more accurate and easier to use, especially since you don’t have to get your hands wet in the process.

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. For our personal tanks, we buy live mangrove seedlings from online websites and then hang them on the side of our aquariums using heavy duty plant wire so that the end of the seedling with leaves is out of water. To ensure that the seedling grows more leaves, we place a dedicated light source on the mangrove. You may have to wipe the leaves of brackish tanks to ensure they can still photosynthesise. Once the mangrove is tall enough, you can plant it in an aquarium with deeper substrate and add root tabs to feed it.

We have also had success with java fern. It had to be gradually acclimated over a period of two to three weeks from freshwater to low-end brackish water (SG 1.005). While the plant has not died, it does not grow very quickly either. Anubias, hornwort and other “brackish” plants are not able to withstand low levels of salinity that is unacceptable for brackish animals. This forum post contains more details about hobbyists’ experiences using brackish water plant.

Java fern (Microsorum pteropus)

How to Set Up a Brackish Aquarium

Most of the instructions are the same as installing a freshwater tank, so we will concentrate on how to make the water. The goal is to reach 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. You can rinse the tank with fresh water, but don’t use soap. For crushed coral and aragonite, you should rinse the substrate many times to avoid any cloudy water. 3. Place the aquarium on the stand, then add the substrate, decorations, and equipment. 4. Dechlorinated water should be added to the aquarium. 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. The methods for cycling a freshwater tank versus a brackish tank are the same (except that plants are not as easily used in brackish water), so read our article on aquarium cycling for more information.

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. For a completely freshwater tank, you will need to follow Step 4a of the instructions. 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. Then use the same method as before to incrementally raise the SG until it matches your established tank. The animals are kept in a quarantine area where salt is added to their bodies. This may result in some parasites or diseases being eliminated.

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

starting concentration of 2 Tbsp of 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 often should you check salinity? We test the SG after every water change, usually within a few hours or the next day.

Bumblebee goby (Brachygobius dorae).

In summary, brackish water tanks can be very enjoyable, especially when you consider all the unique species that you can start keeping. 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.