How to Set Up (and Maintain) a Brackish Aquarium

If you have been keeping freshwater aquariums for a while, you may feel like you’ve already tried everything in the hobby, such as nano tanks, aquascaping, African cichlids, and ponds. 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. Learn what it takes to create and maintain your first brackish aquarium in this step-by-step guide.

Brackish Water Tanks: What are 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

, including:

– 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.

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. Plus, many freshwater diseases and parasites cannot survive in brackish water. 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 freshwater mixes with salt water

Brackish tanks can limit the number of plants and animals 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. 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. We recommend aragonite or crushed coral for soft water with low pH. This will help to buffer the water and recreate a semimarine 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. A refractometer is a device that measures specific gravity (SG) in water to determine the salt content. Although they may be slightly more expensive than a Hydrometer, we believe they are more accurate and more user-friendly, especially as you don’t have your hands get wet.

Refractometer for measuring the specific gravity or amount of salt in the water

What plants live in brackish water? While the internet has many lists of brackish-safe plants, in our experience most plants struggle when salt is introduced. 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). 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

. We personally keep most of our brackish tanks at 1.005-1.008.

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. 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. 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 the refractometer reading, continue adding fresh water and marine salt as needed until the desired SG is 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. 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. Use the same procedure as before to raise the SG incrementally until it matches the 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, Maintain a Brackish Tank and Keep It Clean

Tank maintenance is the same, except that the water preparation is different. 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: 2 Tbsp 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. Premixing the salt and water in a tub or bucket is the preferred method, according to reef salt manufacturers. 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. 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)

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.