Where freshwater and sea water meet
Like all coastal habitats, estuaries, with their surrounding salt marshes and tidal flats, represent a meeting of the land and the ocean. However, perhaps more importantly, as the places where rivers flow into the sea, they are defined by the meeting of freshwater and saltwater, forming a unique habitat where the terrestrial, freshwater and marine converge. This is the recipe for brackish water and are homes to brackish water fish. The more common of brackish water fish seen in the aquarium hobby today originated from coastal estuaries in West Africa, Southest Asia including Singapore and Thailand.
Having been formed as the result of the flooding of river mouths, valleys and their adjacent lands by the sea, by glacial retreat or geological movements, and by the build-up of sediments deposited by rivers, most estuaries are relatively sheltered from extreme wave action and strong currents, but they are nonetheless dynamic environments, which are subjected to both the daily influence of the tides, and the constant input of inland waters. As a result, they are typically characterized by changing water levels, highly variable salinity and a range of temperatures, all of which must be tolerated or overcome by the organisms that live there.
Brackish waters support an abundance of aquatic animal life
Despite the highly variable salinity and range of temperatures, estuary habitats can be counted as being amongst the most productive aquatic ecosystems on Earth; rich in a diverse array of nutrients from both rivers and the sea that supports an abundance of plant and animal species, from photosynthesizing algae and phytoplankton, to invertebrates and fish, birds and mammals, all linked in a complex web of life. In addition to being important feeding grounds, estuaries are also used as nurseries by numerous fish and as breeding and overwintering sites by many birds. Furthermore, their tidal flats and wetlands not only filter large amounts of nutrients, but also potentially harmful pollutants, whilst deposited sediments help to stabilize coastal habitats, protecting them from erosion and flooding.
Fish species included in the brackish water category
A brackish aquarium has the easy maintenance of a freshwater tank but allows the aquarist to raise many unusual fish that are native to more salty water.
The Bumble Bee Goby (Brachygobius doriae) - The ideal set-up is an aquarium with brackish water and plenty of plants and rocks providing the Gobies with ample hiding places. Even though they live in the brackish water, the addition of freshwater will induce spawning.
The Mono Sebae (Monodactylus sebae) - The Mono Sebae is also known as the African Moony and comes from the estuaries and mangroves of the waters of West Africa. The smaller specimens can be kept in freshwater, but as they grow and mature, the water should gradually be converted to a higher salinity. An aquarium substrate consisting of aragonite sand or gravel is preferred. Provide plants and rocks that thrive in brackish water.
The Figure Eight Puffer (Tetraodon biocellatus) - The ideal aquarium will have brackish water with many plants and rocks with plenty of hiding places, and a sandy bottom composed of an aragonite-based sand. Spawning occurs in brackish water.
Salinity level of brackish water
True brackish water is a mixture of three parts salt water to one part freshwater, or 12 grams of aquarium marine salt mixture to one quart of fresh water. Saltwater marine tanks usually contain 4.7 ounces of marine salt per US gallon. A medium brackish tank will have about 2 ounces of marine salt per US gallon, whereas a light brackish tank will have approximately 1 oz of marine salt per US gallon.
The salinity level of a brackish tank should have a Specific Gravity (SG) of no more than 1.021. Full fledged saltwater tanks have a higher SG ranging from 1.021 to 1.026. In a brackish tank the water should be changed about every two weeks. It is important to add salt at these times in order to bring up the levels to where you want them. A hydrometer to measure salinity levels is essential.
This material is provided for informational purposes. It uses material from, "Ocean Revealing The Secrets Of The Deep by Bryan Richard along with other text provided by OCReef staff writers.
« Back To Hobbyist Articles Main Index