Published October 28, 2012
Balloon mollies make great additions to the brackish tank.
If you are new to the aquarium hobby you may not realize just how many different types of aquariums there are. In addition to the basic division of freshwater versus saltwater there are also some options in between. One of the most popular options is the brackish tank. The word brackish refers to a mixture of freshwater and saltwater and this type of water is naturally found in coastal streams, estuaries and saltwater swamps. If you are looking for a unique set-up for your next aquarium or a new challenge as an experienced aquarium hobbyist, you might want to consider starting a brackish tank.
Types of Brackish Tanks
Coastal Stream = A coastal stream is a brackish environment found along coastlines. In these environments there is often little vegetation and the salinity of the water may range from 7 to 14 ppt (a specific gravity around 1.0002). The ideal temperature range for a coastal stream brackish tank is between 72 and 77F and the best pH range is between 7.0 and 7.4. Though a variety of species are capable of thriving in a coastal stream environment, the most common species found in these areas are livebearers such as swordtails, mollies and guppies.
Estuary = An estuary is simply a semi-enclosed body of water that moves very slowly. In order to cultivate an estuary tank, you need to keep the water flow in the tank fairly minimal. The best decorations for this type of tank are sand or gravel substrates, driftwood roots or branches and pieces of water-worn rock. The ideal salinity level for an estuary tank is between 1.020 and 1.025 but it is best to increase the salinity of your tank gradually over an extended period of time so your fish have plenty of time to adjust and so you can achieve stability in your tank. Most estuary tanks are kept at a temperature range between 80 and 82F and at a pH between 7.5 and 8.5. Because it can be tricky to maintain a stable salinity in small tanks, it is best to use a large tank when cultivating an estuary environment.
Saltwater Swamp = The most common type of saltwater swamp used in brackish tanks is the mangrove swamp. These swamps are found in tropical areas throughout the world, particularly in eastern Africa. Mangroves are a type of tree that root and grow in the water but the leaves and branches of the tree grow above the surface. In order to cultivate a mangrove swamp, then, it is best to keep the water level fairly low so the mangroves can grow above the surface. Because mangrove swamps should not be completely filled with water you have the option to stock it with semi-terrestrial species like mudskippers and fiddler crabs. If you plan to keep fiddler crabs, be careful about adding any fish to your tank because they could easily become prey for the crabs. The ideal temperature for a mangrove swamp environment is between 75 and 85F and the best pH level is around 8.0. The salinity level in a mangrove swamp tank may vary, but the ideal range is between 1.005 and 1.01.
Tips for Brackish Tank Set-Up
The key to maintaining a successful brackish tank is to keep the right level of salinity. If the salinity in your tank gets too high, your fish and live plants may fail to thrive. If the salinity is too low, however, species like fiddler crabs may not do well. You have several options when it comes to monitoring the salinity in your tank. You can use an aquarium water test kit or you can purchase a hydrometer which measures the specific gravity of tank water. Before you purchase a hydrometer, take the time to research a few different brands to be sure you get the one that is right for you.
Another important factor in maintaining a successful brackish tank is the type of fish you add to the tank. Not all species of freshwater fish are suited to brackish environments and the mix of freshwater and saltwater is not ideal for tropical saltwater species. Before you select the fish for your brackish tank, be sure to research the individual species to make sure they are compatible with the particular type of environment you want to cultivate. Some species you can consider for brackish tanks include catfish, puffer fish, loaches and gobies. Many livebearers like mollies, swordtails and platies also do well in brackish tank environments.