Brackish waters are dynamic environments where freshwater intermingles with seawater primarily in estuaries, backwater areas and mangrove forests. Brackish water has a salt content greater than freshwater but less than saltwater. There is a tremendously wide range of salinities, and this helps explain why brackish waterways are such diverse ecosystems. In addition to fascinating fish and invertebrates, brackish estuaries are replete with vibrant submerged and emergent vegetation.
Brackish water has a reputation for creating a hostile environment for live aquatic plants. In reality, the reason why some of the plants fail in aquariums are incorrect lighting, inadequate substrate or malnutrition. Sadly, hobbyists are often dissuaded from keeping a planted brackish aquarium and never fully experience the true uniqueness of an estuary biotope. Many readily available aquarium plants are quite capable of thriving in brackish systems. Some are more salt-tolerant than others, and with a little experimentation, it is easy to determine which species are appropriate for your specific aquarium.
Pick a Theme
The first step in establishing a planted brackish aquarium is deciding on the species of fish to be kept and the aquarium’s theme. Brackish fish are very hardy and usually quite active. Some species, such as scats (Scatophagus argus), destroy planted aquariums with their incessant uprooting and penchant for consuming greenery. A deep tide pool theme with unprotected submerged plants is not a good choice for these fish, either. A better option might be to create a shallow Indo-Pacific biotope with mangroves and sturdy marsh plants.
Another excellent theme is a shallow Southeast Asian tributary stocked with a pair of archerfish. I keep an archerfish display, and it is truly amazing watching these fish in action. With about 8 inches of water, a spectacular assortment of both true aquatic and semiaquatic plants can be kept with these gentle fish. Live terrestrial plants can even dangle from above, providing a platform for bugs to crawl on while awaiting the deadly accurate water blast of an unseen predator. I use terrestrial plants like ivy, or philodendron and pothos in my archerfish display. The plants are under the cover (so the bugs can’t climb out) and drape in various levels above the water’s surface. I place crickets and other nonflying bugs on the vines. Some aquariumkeeprs won’t like using crickets or other bugs, but the archerfish need live food, and this is one way to do it naturally.
Acclimating to Brackish Conditions
A significant number of live aquatic plants can withstand water ranging from barely brackish (specific gravity 1.004) to mildly brackish (specific gravity 1.008) conditions. This is an ideal salt range for many brackish fish readily available to the aquarist, such as the tiny bumblebee goby (Brachygobius) and the salt-tolerant mollies (Poecilia spp.).
Just as one would slowly acclimate fish to radically different water conditions, plants also need a smooth transition into brackish water. The sudden introduction of a freshwater plant into a mildly brackish environment would probably result in its death. I recommend starting with a fully cycled, planted freshwater aquarium complete with the fish and plants you wish to keep in brackish water. Over a period of 10 days, using marine salt, slowly increase the salt content of the water to achieve the desired brackishness. Because these fish and plants are often kept at local fish stores in freshwater conditions, simply bringing them home and throwing them into a brackish situation can shock and kill them, hence the gradual 10-day acclimation. The end result is much happier fish and an opportunity for you to observe plants for signs of stress. Plants showing a dislike of the increased salt content can easily be removed and planted in another aquarium where they will recover.
The plants mentioned in the paragraphs to follow have a proven track record of tolerance for mildly brackish water. I am currently growing or have grown all of the plants mentioned and highly recommend them. None of my submerged brackish water plants are grown with CO2 supplementation.
Submerged plants grow entirely underwater but can also have floating leaves and flowers.
Vallisneria spiralis or V. americana. These plants are easy to grow and very resilient. Their long leaves are resistant to all but the most destructive fish. They do not need CO2 supplementation, but they enjoy a nutrient-enriched substrate. Vals grow nicely in water temperatures ranging from 60 to 85 degrees Fahrenheit and do not need intense light. These plants spread rapidly and extend their leaves to the water surface; therefore, they are best planted along the sides or back of the aquarium.
Anubias barteri. Anubias are slow-growing, highly adaptable amphibious plants. They are excellent beginner plants capable of thriving in virtually any lighting and water conditions. Carbon dioxide is not necessary. Anubias grow on logs and rocks, drawing their nutrition directly from the water.
Anubias barteri is particularly appealing to those hobbyists desiring a brackish aquarium with minimal substrate. Their tough leaves render them impervious to all but the most rancorous fish. Anubias do best when kept in 70- to 85-degree water.
Cryptocoryne undulate, C. wendtii. Crypts can survive unbelievable abuse and are ideal for a brackish aquarium. They tolerate low lighting and withstand a temperature range of 68 to 85 degrees. They are sensitive to transplanting and often experience a temporary condition referred to as “crypt melt” when the leaves seemingly melt away. This is not a sign of the plant succumbing; rather, it is adjusting to new water and light conditions. Sometimes hobbyists erroneously think this condition is the result of salt. Cryptocorynes need a nutrient-rich substrate. Carbon dioxide is not required.
Bacopa. These are fast-growing plants that do best in higher-intensity light. Bacopa are ideal for accent points in the aquarium, such as complementing a feature or creating a thicket. Carbon dioxide injection combined with bright light and substrate nutrition make this plant explode with growth. The leaves are tender and susceptible to pecking from larger fish. It grows well in water temperatures ranging from 60 to 85 degrees.
Microsorium pteropus. Commonly known as Java fern, this is the crown jewel of brackish plants. I highly recommend this plant to anyone who thinks they can’t grow live aquatic plants. It is slow-growing, durable and adapts to any lighting conditions. Rather than being rooted in substrate, it lives attached to logs and rocks, and receives nutrition from the water. It is adaptable to water temperatures of 65 to 85 degrees. It favorably responds to higher light and CO2 injection, but neither is necessary.
Marshes are wetland transitional zones where land and water meet. Vegetation typically consists of grasses and shrubs. Emergent growth, such as bog and marsh plants, are rooted in the substrate with stems and leaves extending above the water’s surface.
Marsh aquariums are only partially filled, which allows emergent plants to thrive. They can have a beach area where the substrate is deeply piled up on one end to allow amphibious animals to crawl out the water. For example, my archerfish aquarium is 90 gallons, but it only contains about 50 gallons of water. This allows me to have submerged and emergent growing plants.
Sagittaria lancifolia. This is a beautiful plant with arrowhead-shaped leaves. It is ideally suited for an open-topped marsh aquarium. Sagittaria lancifolia can grow taller than 3 feet outdoors but usually peaks at about 18 to 24 inches indoors. Because this is a true bog plant, it does best in a nutrient-enhanced substrate.
Sagittaria subulata. This beautiful plant grows to about 6 inches and is perfectly suited for a bog (marsh) aquarium. Plant it in about 2 to 4 inches of water and provide moderate to bright lighting. Sagittaria subulata feeds heavily from its roots (as opposed to the leaves) and probably will require iron supplementation. Provide a plant-specific substrate. Water temperatures for this plant range from 64 to 85 degrees.
A swamp generally has better drainage than a bog and contains trees and other woody plants.
Rhizophora mangle. Also known as the red mangrove, this plant is able to thrive in fresh, brackish or total saltwater. The red mangrove has a unique ability to filter out the salt and only draw freshwater. It can be rooted in a fertile substrate or affixed to an object (an emerged log) several inches above the substrate. The affixed plant will extend roots that will lengthen and thicken into prop roots that these plants are famous for. Prop roots are aerial extensions from the plant’s stem that grow down into the substrate. It gives the plant the appearance that it is growing on stilts. These unique structures help to brace the plant, especially in tidal areas where tremendous water turbulence is encountered.
Mangroves cannot survive completely submerged and must at least have their leaves above the water surface. An open-topped aquarium with bright lighting is ideal. Carbon dioxide supplementation is not required since the plant is able to absorb as much of this nutrient as it needs from the atmosphere. Mangroves are slow-growing but well worth the effort. You will not be disappointed.
The recent interest in brackish aquariums has propelled this intriguing aspect of our hobby from niche to mainstream status. Planted brackish aquariums are easy to keep and always draw interest. Begin your planted aquarium by choosing two or three of the easier plants previously mentioned, and slowly transition your aquarium to create a unique biotope.