How to Set up (and Maintain) A Brackish Aquarium

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. Although many aquarists are nervous about creating brackish water from freshwater tanks, we believe it is possible. This step-by–step guide will help you create and maintain your brackish aquarium.


Brackish Water Tanks: What are the Pros and Cons?

Let’s take a look at the pros and cons of this new venture before we jump into it. Brackish aquariums offer the opportunity to:

keep new kinds of 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 can try breeding amano shrimp and nerite snails, whose offspring only survive in brackish water. 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.

Brackish aquariums are not dependent on a specific amount of salt. Brackish species can adapt to changing conditions unlike corals in saltwater aquariums. This is because they live near rivers and streams that meet the ocean. The tides and rainfall can affect whether they receive fresh or salt water in 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 in California where fresh water 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). Salt creep and leftover salt residue may occur in areas that water has escaped from the tank. To mitigate this, you can either wipe it off with damp cloths or put craft mesh around the tank lid holes.

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.

You must purchase marine salt for saltwater aquariums and not the regular aquarium salt for freshwater. While aquarium salt is sodium chloride (NaCl), marine salt has sodium chloride as well as many essential minerals like magnesium, potassium and 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 is used to determine the specific gravity and amount of salt in 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. To ensure that the mangrove can continue to photosynthesize in brackish aquariums you might need to periodically wipe off salt spray. Once the mangrove is tall enough, you can plant it in an aquarium with deeper substrate and add root tabs to feed it.

Java fern is another plant that we have had success. 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. 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. The goal is to reach 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. Rinse the tank and accessories in fresh water without using soap. If using aragonite or crushed coral, make sure to rinse the substrate multiple times to minimize cloudy water issues. 3. Add the decorations, equipment and substrate to the aquarium. 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. 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. 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. 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, Maintain a Brackish Tank and Keep It Clean

The steps for tank maintenance are identical, except that of the water preparation. 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

, that means you will need to add back in 10 gallons of dechlorinated water and 20 tablespoons (or 1 1/4 cup) of 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. The salt dissolves quickly so you can either mix the water by hand or add an airstone to get large amounts 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. We like to dump it around the filter output or power head for faster distribution. 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.