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. Learn what it takes to create and maintain your first brackish aquarium in this step-by-step guide.
Brackish Water Tanks: The Pros and Cons
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:
Conserve new aquatic species
– Green spotted puffer, (Dichotomyctere.nigroviridis); – Figure 8. puffer (Dichotomyctere.ocellatus/Tetraodon biocellatus); – Bumblebee flyby (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
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.
Brackish aquariums are not dependent on a specific 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 in California where fresh water mixes 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. You will need to take extra steps to maintain your tank. These include adding the correct amount of salt, and measuring the specific gravity of the water. 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 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.
You must purchase marine salt for saltwater aquariums and not the regular aquarium salt for freshwater. 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. They are slightly more costly than a hydrometer but they are easier to use and more accurate.
Refractometer for measuring the specific gravity or amount of salt in the 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. We know of only one plant that can handle salt water, and that is the mangrove tree. To make our own tanks, we purchase mangrove seedlings via online sites. We then attach them to our aquariums with heavy duty wire. Once it starts growing more leaves, we have a dedicated light source shining on the mangrove to make sure it gets enough light. 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. It had to be gradually acclimated over a period of two to three weeks from freshwater to low-end brackish water (SG 1.005). Although the plant has not died yet, it doesn’t seem to be growing very fast. 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. 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. You want to get to 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. 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 upon the reading of the refractometer, add more water and salt until you reach the desired SG.
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. There are no differences in how to cycle a freshwater or brackish tank. But plants can be used more easily in brackish. Read our article on aquarium recycling.
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. 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
The steps for tank maintenance are identical, except that of the water preparation. Salt is removed during water changes so you need to track how much water was taken out in order to maintain the salt level. 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 that you will need to add in 10 gallons worth of dechlorinated liquid and 20 tablespoons (20 or 1 1/4 cups) salt. The preferred method recommended by reef salt manufacturers is to premix the water and salt in a bucket or tub. 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. 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 do you need to test your salinity? Every water change is a good time to check the SG. Usually, it’s within a few hours or 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.