There are many and diverse species of true aquatic, bog and near-water brackish plants suitable for semi fresh/marine aquarium use. And not surprisingly, it follows/is coincident that most brackish water fishes and invertebrates greatly prefer/benefit from the presence of these true/vascular plants. Live brackish water plants fulfill the same functions and aesthetics as with freshwater planted aquariums and "reef" type marine set-ups... The plants condition, stabilize water conditions, provide food, habitat, and are good looking.
There are a few "rules" re brackish water plant use beyond simple selection and placement. Here we'll introduce the basics of their use including review of the varieties the hobbyist is most likely to be able to locate for their brackish system/s.
First Off, A Few Necessary Definitions:
What do we or at least I mean by "brackish"? Some "in-between" concentration beyond "freshwater" (almost all freshwater sources have appreciable salts in them) and typical seawater (most seawaters have about 3.5% salt content, or a specific gravity of approximately 1.025. Many pet-fish writers include specific values, so we will as well. In the way of spg, brackish systems have water with salt content between 1.005 and 1.012.
In chemistry (please bear with me, I am an old H.S. Science teacher), salts are combinations of metals and non-metals, ionic compounds. Some examples: sodium is a metal, chlorine a non-metal halogen... together they're sodium chloride, aka table salt. Magnesium is a metal, sulfate (a Sulfur, and three oxygen atoms) a non-metal radical... together they're magnesium sulfate, Epsom salts...
I have seen a few articles in recent years that state "any salt" is okay to use to make brackish water from fresh, examples given include table (iodized or not), kosher, ice cream salt (these are all principally sodium chloride). I caution and advise against these uses and encourage you to either use mixed in "real" seawater or a synthetic seawater mix for your brackish/salt additions. Here's an important exception. IF you're simply adding some/more salt to a freshwater system, on the order of a teaspoon or so per gallon, the "other" simpler salts are fine to use. Seawater has about twelve teaspoons of a combination of many salts (the preponderant one of which is sodium chloride). The mix, blend of other ions in real seawater or its facsimile are important to real/true brackish livestock (fishes, invertebrates, plants, microbes...). Your system will be healthier, more stable using real or faux seawater blended in with fresh.
There are some thallophytes, algae, that look like true/vascular plants... for the most part these are undesirable forms that are best controlled by the cultivation of the true plants (Kingdom Metaphyta). As with selection of freshwater aquarium plants, one must be on their guard, aware that what are sold as "true aquatics" are often cuttings, growths of "bog" plants or worse, terrestrial growings that have been dunked underwater. Study of appropriate species, examination of stocks (e.g. for presence/location of stomata) is essential.
Rates of Change/Acclimation:
As with experiments and practices of conversion of tolerant "freshwater" fish livestock to saltier environs, most plants have known ranges AND rates in which these changes can be made safely. When, where in doubt, do consult reference works re both these aspects, measure the water your plants are currently growing in, and acclimate them slowly (a thousandth of spg per every few days) to your systems water density. Similarly, check for yourself what the ambient pH, hardness/alkalinity and temperature of the systems you're moving your livestock from are and adjust these slowly.
More and Less Brackish Water Aquarium Plant Species:
You'll likely be surprised at how many common aquarium plants are to some degree brackish. Most all do tolerate salts to some extent. On the most successfully kept species you will find notes and a last list below... All those listed can do okay to well at the lower end of brackish range... near densities of 1.005.
The groups and species presented below are all recorded as brackish-useful in the literature (pet-fish and scientific). The "best" list following these categories are ones I have kept in such circumstances.
Best/hardiest brackish water plant species I have used: Microsorium pteropus, Hygrophila polysperma, Sagittaria spp., Vallisneria spp., Echinodorus tenellus, Ceratopteris spp.,
Like their so-called freshwater counterparts (often the same species), brackish plant cultivation calls for regular fertilization with complete preparations and possible soil addition (fine, w/ clay) mixed into the lower gravel/substrate area. Stumped as to why your plants won't/don't grow? Why their leaves are yellowing? How to make them more luxurious. Often these are matters of too little (sometimes too much) of "something". Help is available. Visit "the krib" on the Internet for troubleshooting information and common-sense solutions (link below).
I trust I've made a large and often enough mention of the benefits of pre-making and storing new/make-up water... In these times of vacillating tapwater quality, there is no better, cheaper, safer way to assure that the watery environment you're re-supplying is about what you want it to be than to utilize a dedicated container like a plastic trash can, pump, heater... to have new water ready on hand.
Due to most hobbyists' insatiable desire to overstock, overfeed their systems, many brackish tanks are downright turbulent in their water movement. Bear this in mind when placing pumps, airstones, picking out gravel types/grades, placing your green livestock... that your plants may be overly buffeted about by such circulation.
Some authors on brackish topics suggest that these environments are more/less tropical than the seas they border... Some are both depending on the seasons... For the most part I suggest setting your systems' temperatures on the lower side of the livestock's known ranges to slow down their metabolisms (less food, wastes, longer lives... more gas solubility.) with once again, consulting references on each species preferences, tolerances.
About Brackish Water Plant Eaters:
As yet we haven't mentioned the palatability of live plants and fishes. Rest-assured, some brackish water animals are pure terrors with plantings. Scats for instance, revel in eating and uprooting any and all plant stocks. Soft, easily torn varieties are out when keeping these fishes. Alternatives exist for keeping the plants and there would-be consumers apart. Iit's not difficult to grow your plants in either a tied-in sump arrangement, just moving water back and forth between the fishes and plants areas, or to place tastier varieties behind a glass or plastic partition.
Do brackish systems absolutely require live plants to be successful? Strictly speaking no. The benefits of using live plant material can be supplied in other ways. As food, brackish fishes do engage in eating "their" plants... expect this. If you don't supply living sources, "green" foods can be supplemented. For shade? Other decor items can be used. For waste removal, supplying oxygen... yes, filtration can be boosted, maintenance done religiously.
For a "complete" look and set-up however, as with all-freshwater systems, there is nothing like live plants to complete a brackish water display. Do consider them if you get try brackish aquarium keeping.
Bibliography/Further Reading: General
Anon. 1975. Tanks with brackish or mixed water. Aquarium Digest Intl. 3:4, 75.
Anon. 1981. Where water worlds mingle. Aquariums Australia 2:1, 89.
Baensch, Hans A. & Rudiger Riehl. 1993. Aquarium Atlas, v. 2. BAENSCH, Germany. 1212 pp.
Brunner, Gerhard. 1973. Aquarium Plants. T.F.H. Publications, NJ. 159 pp.
Burgstaller, B.J. 1978. The brackish system. FAMA 8/78.
Dawes, John. 1989. Bolstering sales of brackish water fish. Brackish water fish are undersold in most pet stores, even though some of the commoner aquarium specimens are brackish species. Pets Supplies Marketing. 7/89.
Gibbs, Max. 1995. The brackish aquarium. FAMA 4/95.
Gos, Michael W. 1977. The brackish aquarium. TFH 10/77.
Gos, Michael W. 1980. The brackish system, part 1: Setting up. FAMA 11/80, part 2: Inhabitants 12/80.
James, Barry. 1986. A Fishkeeper's Guide To Aquarium Plants. Salamander Books, U.K.. 117 pp.
Radford, Albert E. 1986. Fundamentals of Plant Systematics. Harper & Row, NY. 498 pp.
Raven, Peter H., Ray F. Evert and Helena Curtis. 1976 2d ed.. Biology of Plants. Worth Publishers, Inc., NY. 685 pp.
Riehl, Rudiger & Hans A. Baensch. 1987. Aquarium Atlas, v. 1. MERGUS, Germany. 992 pp.
Riehl, Rudiger & Hans A. Baensch, 1996. Aquarium Atlas, v. 3. MERGUS, Germany. 1103 pp.
Roe, Colin D. 1967. A Manual of Aquarium Plants. Shirley Aquatics, England. 111 pp.
Stemmermann, Lani. 1981. A Guide to Pacific Wetland Plants. U.S. Army Corps of Engineers, Honolulu. 118 pp.
Stodola, Jiri. 1967. Encyclopedia of Water Plants. T.F.H. Publications, NJ. 368 pp.
Taylor, Edward C. 1982. Keeping a brackish aquarium. TFH 5/82, part 2: livestock. 6/82
Taylor, Edward C. 1996. Creating a brackish-water biotope. Pet Business 11/96.
Volkart, Bill. 1989. The brackish aquarium: Part 2, plants. TFH 7/89.
Wickham, Mike. 2001. A pinch of salt. Brackish aquariums offer a new wrinkle to fishkeeping. AFM 10/01
DeFiore, Tony. 1999. Are Anubias for you? TFH 7/99.
Gasser, Robert A. 1978. Anubias barteri. FAMA 9/78.
Gasser, Robert A. 1979. Anubias nana. FAMA 11/79.
Gartner, Otto. 1987. A visitor from Southern Nigeria, Anubias hastifolia. Today's Aquarium 4/87.
Randall, Karen A. 1996. Care and propagation of Anubias. The Aquarium Gardener 9:3/96.
Randall, Karen A. 1996. Anubias. Looking for live plants? Try these. AFM 11/96.
Randall, Karen. 1999. Aquatic Horticulture: More Anubias. Aquarium Frontiers 5/99.
Randall, Karen. 1999. Aquatic Horticulture: Anubias barteri. Aquarium Frontiers 3/99.
Rataj, Karel. 1981. Anubias lanceolata, a large tank plant. TFH 4/81.
Rataj, Karel. 1986. Anubias congensis. A look at one of the largest of the popular plant genus Anubias. TFH 5/86.
Stevenson, Anna. 1993. Anubias barteri Schott. The Aquarium Gardener 6:2/93
Ranelli, Jack. 1987. Bacopa amplexicaulis and monnieri. FAMA 1987.
Rataj, Kaerl. 1974. Bacopa monniera. TFH 10/74.
Wischnath, Lothar. Undated. The Bacopas- plants for every aquarium. Aquarium Digest International #26
Hartman, Pat. 1986. The propagation of Cabomba; or a dissertation on bunch plants. The Aquarium Gardener 1(2):86.
Rataj, Karel. 1982. Cabomba piahyensis. TFH 1/82.
Rataj, Karel. 1985. A rare Cabomba- Cabomba australis. TFH 10/85.
Kasselman, Christel. 1994. Decorative aquarium plants: Hygrophila polysperma (Roxburgh) T. Anderson. The Aquarium Gardener 7:4, 94 (DATZ reprint)
Rataj, Karel. 1986. The big and beautiful Hygrophila angusitfolia. TFH 12/86.
Rataj, Karel. 1988. Hygrophila polysperma: classic aquarium plant or newcomer? TFH 2/88.
Anon. 1992. From the land of Java, Microsorium pteropus, the Java Fern. FAMA 6/92.
Coletti, Ted. 1995. Java Fern: The perfect aquarium plant. TFH 12/95.
Brown, Philip J. 1976. The Java Fern, Microsorium pteropus. TFH 9/76.
Whiteside, B. 1970. A fern for the aquarium. The Aquarium 11/70.
Wilkens, Peter. 1975. Some additional observations on the cultivation of Java Fern (Microsorium pteropus). Aquarium Digest International 3:4,75.
Paffrath, K. Undated. The Brazilian milfoil- an amphibious plant to enhance any aquarium or garden pool. Aquarium Digest Intl. #37.
Rataj, Karel. 1983. Myriphyllum hippuroides, a beautiful watermilfoil. TFH 3/83.
Wischnath, Lothar. 1989. Some unusual Myriophyllum species. TFH 12/89.
Anon. 1992. The Sagittaria of arrowhead. Reprinted from Mulertt's THE AQUARIUM (January, 1893). The Aquatic Gardener 5(4):7,8/92.
Anon. 1994. The origin of Sagittaria natans. Reprinted from Mullertt's THE AQUARIUM (April, 1896). The Aquatic Gardener 7(3):5,6/94.
Paffrath, Kurt. Undated. Sagittaria graminea- a very variable species. Aquarium Digest Intl. #36.
Paffrath, Kurt. 1985. Portrait of a pond plant; the common arrowhead Sagittaria sagittifolia. Today's Aquarium-Aquarium Heute, 4/85