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. 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 help you create and maintain your brackish aquarium.
The Pros and Cons of Brackish Water Tanks
Let’s take a look at the pros and cons of this new venture before we jump into it. Brackish has the advantage of being able to
Keep new species of aquatic animals
– Green spotted puffer (Dichotomyctere nigroviridis) – Figure 8 puffer (Dichotomyctere ocellatus or Tetraodon biocellatus) – Bumblebee goby (Brachygobius spp.) – Knight goby, Stigmatogobius sadanundio – Mudskipper, Periophthalmus species 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.
Brackish water has many benefits for livebearers. It contains all the water parameters and trace minerals necessary to sustain 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. 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 fresh water is mixed with salt water
Brackish tanks, however, do restrict the kinds of animals and plants that 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). 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. 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 from sodium chloride, but marine salt contains sodium and other essential minerals such as magnesium, potassium, calcium. A refractometer is a device that measures specific gravity (SG) in water to determine the salt content. 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 for measuring the specific gravity or amount of salt in the water
Which plants can live in brackish waters? Although the internet is filled with lists of brackish-safe plant names, we have found that most plants will struggle to withstand salt water. Mangrove trees are the only plant that can withstand saltwater, even full fresh. 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. 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.
We have also had success with 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. The plant is not dead, but it doesn’t grow fast. Other “brackish”, such as anubias or hornwort, can only handle very low salinity levels, which is not acceptable for most brackish species. For more information on hobbyists’ experiences with brackish water plants, see this forum post.
Java fern (Microsorum pteropus)
How to Set up a Brackish Aquarium
The instructions for installing a freshwater aquarium are similar, so let’s focus on how to prepare it. It is important to achieve a
specific gravity between 1.004-1.012
. Personaly, we keep the majority of our brackish tank at 1.005-1.008.
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. For crushed coral and aragonite, you should rinse the substrate many times to avoid any cloudy water. 3. Place the aquarium on the stand and add the substrate, equipment, and decorations. 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. You can get brackish water right from the beginning by filling 80% of your tank with fresh water. Next, add 2 tablespoons (2 Tbsp) reef salt to each gallon. Let the filter or powerhead circulation dissolve the salt, and then check the specific gravity after approximately 8 hours. 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. To set up a freshwater aquarium, follow Step 4a. 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. Some parasites and diseases can be eliminated because the animals are being kept in quarantine.
Banded archerfish (Toxotes jaculatrix)
How to Change Water and Maintain a Brackish Water Tank
Tank maintenance is the same, except that the water preparation is different. Because salt is taken out during water changes, you must keep track of how much water is removed to keep the salinity the same. For example, let’s say you decide to do a 50% water change on a 20-gallon aquarium.
Based on our
Starting concentration: 2 Tbsp salt per gallon
This means that you’ll need to add 10 gallons dechlorinated water, 20 tablespoons (or 1 1/4 cups) 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. Marine salt dissolves very quickly, so either stir the water by hand, add an air stone, or use a power head to mix together large volumes of water. 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. To speed up distribution, we prefer to pour it around the filter output and power head. 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 doriae
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.