Establishing a Brackish Water Aquarium
The basic rules that have been discussed concerning other types of aquariums apply equally to brackish water tanks. Just as freshwater aquarium experience is a useful asset for those seeking to keep marine animals, keeping estuarine species will help prepare you for the challenges posed by more delicate captives.
In sharp contrast to the stable conditions encountered by marine organisms, brackish water fish and invertebrates experience daily changes in salinity, water level, and pH. These animals are, therefore, often quite resilient captives. As discussed in the species accounts, some such creatures actually benefit from salinity fluctuations. While few brackish water animals regularly breed in home aquariums, it does seem likely that such fluctuations might also be necessary to stimulate reproductive behavior.
Most brackish water animals will thrive at a specific gravity of 1.005. This should, for most organisms, be allowed to fluctuate from time to time. Safe parameters for the most commonly kept species seem to be between 1.002and 1.007. Of course, these figures are general in nature, so be sure to learn as much as you can about the animals in which you are particularly interested. There is an array of fascinating estuarine fish and invertebrates that have rarely been maintained in captivity, so interested hobbyists have a real opportunity to add to our overall knowledge.
Although many estuarine animals can tolerate marine water, the most commonly kept species spend most of their time in water that is considerably less saline. The safest salinity level is approximately 1.005, which is roughly equivalent to 1 gallon of seawater dissolved in 4 gallons of freshwater.
Most brackish water fish are extremely active animals and, consequently, require highly oxygenated water. When setting up your filtration system, be certain that the water returned to your aquarium activates the surface well, or add additional air stones.
Estuarine animals generally fare well at a pH of 7.6.
Most dealers and pet stores maintain brackish water fish in either freshwater or saltwater, depending upon the species. Orange chromides are, for example, usually kept in freshwater aquariums, while monos are often exhibited with marine fish. Although they will survive under these conditions, most will not exhibit normal behavior or attain their brightest coloration. You should take note of how the fish that you purchase have been maintained, as the salinity and pH at your own brackish water aquarium will likely be very different. Even though most estuarine species are quite hardy, you should err on the side of caution and introduce them slowly into your aquarium.
Although plants specifically adapted to brackish water environments are not at all common in the trade, mangrove seedlings are becoming increasingly available. Certain aquatic plants that are usually grown in freshwater aquariums may also survive in mildly saline waters. In general, the freshwater plants that fare best are those with waxy leaf coverings, such as the various grasses of the genus Vallisneria, the giant sagittaria,
A number of brackish water fish and invertebrates are best exhibited in aquariums only partially filled with water, and equipped with a land area. Fiddler crabs, archerfish, four-eyed fish and mudskippers will all exhibit their unique behaviors to their best advantage in such aquariums. There are a number of ways to establish a land area. The simplest is to create a land area of rock or coral. While this will suffice for some species, others do best when provided with an actual mud or sand beach.
A beach area may be established by installing a glass barrier in your tank to separate the substrate from the water, or by simply using a separate plastic container within the aquarium. Alternatively, a number of custommade terrariums incorporating land and water areas are becoming increasingly available at pet stores. Be sure that the beach is readily accessible so that you are able to clean it and replace the substrate.