» Posted by on Feb 27, 2015 in Blog, Cyndi T, Education, Freshwater Fish | Comments Off on Tropical Fish to Buy: The Brackish Aquarium

Brackish Fish for Sale – Absolutely Fish, NJ


Tropical Fish to Buy: The Brackish Aquarium

By Cyndi Taylor


Are you a seasoned aquarist looking for a different kind of tank? Do you think those Figure 8 puffers are way too cute to pass up? Is a saltwater tank still too daunting to set up? Perhaps a brackish water tank is right for you! Brackish water can be found where a river meets the ocean, also known as an estuary. This means that the salty water from the ocean mixes with the freshwater from the river, creating an array of different salinities in the estuary. Salinity can be measured by the specific gravity, the density of salt found in 1 liter of water, usually measuring out to be 1.022- 1.024 in saltwater aquaria. Freshwater has no salt, so the SG reading would be 1.000. Brackish water can therefore be anywhere between 1.005 (low end) to 1.021 (high end) SG. How much salt to add all depends on what fish you would like to keep; however most brackish water fish are very adaptable. Here’s how to set one up:

First, research exactly what fish and plants you would like to keep in your new brackish aquarium (some species will be listed below). Now that the maximum size of the fish is known and the appropriate size tank can be set-up. The set-up is very much like a freshwater tank, however, make sure the equipment you buy is for both fresh and salt water use. Any filter will be fine; preferably one rated a size larger than the tank size. Instead of gravel, you may consider using crushed coral or an aragonite sand to help buffer the water and keep the pH between 7.8 and 8.4. The temperature should be kept around 78° Fahrenheit.

Next, add marine salt (NOT aquarium salt!) to the water, following the instructions to get to a SG of around 1.005 (measuring with hydrometer), again depending on the fish. Always mix salt into the bucket of water first and then add it to the aquarium to prevent any extra stress to the fish. It is best to start at a lower salinity with small fish and gradually increase the salinity months at a time until you reach the desired amount. You must start with salt in the water when you begin the nitrogen cycle! Any drastic increases or decreases in salinity will destroy the nitrifying bacteria established in the tank. The fish may be easily adaptable to salinity changes, but the nitrifying bacteria in the aquarium are not as adaptable. Therefore, you must have salt in the water when the cycling process starts in order to not have bacteria die off later. The nitrogen cycle will still take about a month or longer to complete, and then your tank will be ready for the next round of fish!
OPTIONAL: If you would like to add bacteria to the tank as you add your first batch of fish, Dr. Tim’s One and Only claims that the freshwater version would be good for water with a SG of 1.007 or under and the saltwater version is for any SG above 1.007.

The cool thing about brackish water are the many different and unique species of fish and invertebrates to choose from. Many of these species are able to live in pure freshwater for a bit, as they have adapted to do so in nature, but they will soon need salt added to the water. Some fish will even need a full marine specific gravity as it grows to an adult. Here are a few species we normally carry in our brackish water tanks:

Bumble Bee Goby: Brachygobius doriae:

Marine Invertebrates for Sale New Jersey - Bumble Bee Goby

Bumble Bee Goby

This little yellow and black striped cutie can be found, usually, with our pea puffers; however they do prefer a bit of salt in the water. Specific gravity should be around 1.005. Getting no larger than 2 inches, these little gobies are territorial, so buy them in groups of about 6 to help spread the aggression around. Provide plenty of small caves and plants to help with the aggression issues. They may be a bit of a fin nipper, so do not mix the gobies with any fish with long fins. For food, small frozen foods like reef plankton or bloodworms will work best with these picky eaters.


Figure 8 Puffer: Tetradon biocellatus:

Marine Invertebrates for Sale New Jersey - Green Spotted Puffer

Green Spotted Puffer

This small brown and yellow–green puffer is a nice choice for a smaller aquarium. The puffer only grows to about 2.5″, making it one of the smaller species of puffers. Puffers are generally aggressive fish, however, the Figure 8’s can be considered a more docile species. They are best kept alone in at least a 15 gallon tank. If planning to keep more, have about 10 gallons of water for each puffer to give them some space. Some aquarists have kept these puffers with Mollies, Knight Gobies, and Bumble Bee Gobies with success. They are considered to be a low end brackish fish, needing about 1.005 to 1.008 SG. Diet should include snails, clams, or anything with a shell to scrap its tooth on.


Red Chromide: Etroplus maculatus:

Marine Invertebrates for Sale New Jersey - Red Chromide

Red Chromide

This orange cichlid from India is a great choice for a mid size tank, about 30 gallons. Maximum size is about 3″. They are generally peaceful, but they are a cichlid, so buy them in groups of 3 or more to help keep aggression low. As for salinity, they can be in either fresh water or low end brackish, so keep the SG at no higher than 1.008. In the wild, the Chromide have been seen to graze on algae, so be sure to incorporate algae foods, like spiralina into its diet.


Mono: Monodactylus sebae:

Marine Invertebrates for Sale New Jersey - Monos

Mono Sebae is on the left

No these are NOT angelfish, but rather the “African Moony” from West Africa. They are a large growing schooling fish, so a big tank of at least 75 gallons is necessary for swimming space. Their maximum size is 8″. Juveniles can live in freshwater, but as they mature they need a gradual increase of SG to 1.022 when they reach adulthood. However in their “teenage years” you may keep them in a brackish tank. Their temperament would be considered semi-aggressive, like a large barb. Monos’ diet should include algae based foods to replicate what they eat in the wild.


Nigerian Mudskipper Periophthalmus barbarus:

Marine Invertebrates for Sale New Jersey - Mudskipper


You can find these unusual fish from Africa in our paludarium tank in store. Due to their foraging behaviours, mudskippers need a land part in their tank to mimic their natural environment. Despite having gills, mudskippers have evolved to breath air through their skin by having a network of capillaries that let oxygen diffuse into their bloodstream and releases carbon dioxide, like a frog or salamander. This is known as cutaneous respiration. Their maximum size is around 6″. Two mudskippers would need at least a 20 gallon tank that is about 2′ long. Add another 10 gallons for each addition mudskipper. The water should be at a SG of between 1.005 and 1.015 and have a depth of about 4 inches. The tank should have a beach like look for the substrate being used. Mudskippers are carnivorous, but accept a wide range of foods from freeze dried plankton to even pellets. Beware as they may eat smaller fish.

These are only a few highlights of the different species you are able to keep in a brackish aquarium. Others include: Scats, Mollies, Knight Gobies, Archer Fish, Glass Fish and more! For more information about these hidden gems in the freshwater section, please ask an associate at Absolutely Fish for information and guidance through the brackish world!  

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