Marine Aquarium Plants 

5 star fish offers access to a very wide selection of nice live saltwater aquarium plants. Besides adding an attractive splash of color to the aquarium, they are very helpful in maintaining a healthy tank environment. Some marine tank plants are very affordable, and some are a bit expensive but most will grow and spread in the tank.

Some benefits of keeping live marine aquarium plants are as follows:
• Remove nitrates & phosphates, thus reducing the occurrence of nuisance algae.
• Provide a continual supply of live natural food for grazing fish & invertebrates.

Saltwater aquarium plants remove nutrients from the aquarium such as nitrates and phosphates, this in turn makes the tank safer for sensitive inhabitants such as corals. This also removes nutrients that would otherwise fuel the growth of unwanted algae.
These live plants also provide food & shelter for zooplankton such as copepods & amphipods, these in turn serve as a continuous supply of live food for sea horses, corals, mandarin fish, and other plankton eating tankmates.  Some plants can be places directly in your aquarium to make a beautiful, natural and interesting display. Depending on their tankmates it is often best to place them in a separate refugium where they are safe from plant eating fish and invertebrates. Alternative a tank dedicated to live marine plants and compatible tankmates is also attractive and doable.

MOST PLANTS OFFERED HERE ARE SMALL FRAGS ABOUT AN INCH TALL. 

Here is an extensive list of clickable links to popular marine aquarium plants offered on Ebay. 

Caulerpa racemosa (Grape Caulerpa)
Caulerpa Peltata (Similar to Grape Caulerpa)
Caulerpa taxifolia (Feathery Caulerpa) Mexican Varity 
Caulerpa prolifera
Codium
Dragons Breath
String of Pearls
Galaxaura 
Red Grape Caulerpa 
Birds Nest Gracilaria
Golden Sargassum Seaweed
Mermaids Fan
Mermaids Shaving Brush
Halimeda
Gracilaria Laruis

Ant here is a list of marine aquarium plants offered on Amazon. 

Caulerpa taxifolia Caulerpa prolifera and some other Caulerpa macro algae plants are some of the most popular macroalgae for the saltwater aquarium. Many green marine macro algae will spread in the tank and produce a beautiful graceful garden swaying in the currents.
I have seen amazing reef tanks where the main backdrop was not live rock or coral, but was a wall of various live saltwater plants.
According to the Marine Atlas, Volume 1, Caulerpa has been shown to release substances into the aquarium water that help to naturally ward off diseases in marine fish.

Some red macro algae are so unusual and beautiful that they resemble coral.

Hypnea macro algae (Hypnea Pannosa)
is an amazing blue algae.

Purple Fauchea  (Fauchea Sp.) This is a bueatful and rare macroalgae.

Barbed Heart Macro algae

Red Razor (Bryothamnion Triquetrum)
Red algae plant. This offer is for one plant.

Orange Starburst   Euchema Spinosum

Red Bush Gracilaria Hayi From Algae Nursery

Red Bush Gracilaria Hayi
From Aquacultura Nursery Farms

Bryothamnion Red Razor Macro Algae

Sea Lettuce Ulva Sp

Tufted Joint Algae

Live Sea Grass possible Syringodium filiforme or similar species.

Hawaiian Ogo Plant

Chaetomorpha                  Mangrove seedlings

In the refugium or a well lit sump area Chaetomorpha algae and
Red Mangrove tree seedlings are popular. Neither of the two are very attractive in the tank itself, but the do a great job of removing
nutrients from the tanks water as it the water passes through your sump or refugium hidden under or behind the tank. Chaetomorpha algae is very hardy and is the perfect habitat for amphipods and other plankton in your refugium.

Plankton
If you are putting plants in your refugium then it only makes sense to also stock it with zooplankton. The zooplankton will breed among your new reefugeium plants and provide a constant source of biodiversity and live food to your reef tank.
Try the above mixture of 6 kinds of live Phytoplankton or microscopic algea cells combined with 5 types of zooplankton.

The kit above includes these 5 species of live saltwater copepods.
Parvo
Acartia
Pseudo
Tisbe
Tigger Pods
They are tiny and range in size from 20 microns to 3 millimeters.
The above kit also includes these 6 strains of Phytoplankton or microscopic algae to serve as food for the copepods.
Isochrysis,
Tetraselmis,
Nannochloropsis,
Pavlova,
Thalassiosira,
Synechococcus.

Compatibility Concerns
Marine plants will be quickly eaten by some but not all reef tank inhabitants. Some fish and many urchins will consume your plants before you know what happened. Do research on what your tanks inhabitants eat and stay away from plant eating herbivores like tangs, parrot fish, blennys, sea urchins, turbo snails, and sea hares. If you are not sure if your tank inhabitants will be safe with plants then start with a few plants and see if they survive, if they do then they will likely thrive and then you can try other verities.

Additives: For marine aquarium plants it may not be necessary but you can experiment with the use of aquarium plant additives regularly. Marine plants that feel hard to the touch such as Halimeda and calcareous algae contain calcium, thus an aquarium additive containing calcium will be helpful. All marine plants respond very well to aquarium iron supplements and aquarium iodine supplements.

Circulation: Most marine plants seem to do well in areas with some circulation. This is true both in reef tanks and in the wild. Powerheads provide more than enough circulation, but wavemakers do so while also providing a more random natural looking and rhythmic movement in the tank.

Lighting: Some things to consider about keeping live marine plants is that they required good quality marine aquarium plant lighting, 
Standard reef tank lighting that equates to about four or more watts per gallon can work for saltwater plants. But reef tank lights are designed to simulate the blue light that penetrates deeper in to the oceans waters, say 30 to 100 foot deep very roughly where corals grow. These lights produce lots of blue light most in the range of 10,000 to 20,000 kelvin.
As stated above marine macro algae will grow under reef tank lights that simulates light in coral reefs several yards deep. In nature most marine plants grow in shallower water than most corals. Often the plants grow in water that is just a few foot deep. Marine plants are adapted to utilizing whiter shallow water light in the 6500 kelvin rang. 6500 k light is what we encounter on land or in very shallow water. This type of light is used for growing house plants and plants in freshwater planted aquariums. This light looks bright, white, crisp, and very natural. Saltwater plants will grow better under these aquarium plant lights. Saltwater aquarium plants also look better under these freshwater plant lights. In fact some coral lights are designed without the colors of lights that plants need. This is done to deter unwanted plant growth, (we are taking about nuisance algae.) You may want to consider whiter fresh water planted aquarium. They do not have to be exactly 6500 kelvin, 7000 k or 7500 k will qualify as being in this range. If the aquarium has enough light for plants and corals, but does not have as much blue light as a typical reef tank, then some low light corals such as mushrooms and polyps, as well as sea anemones, are often housed in marine planted tanks. Also didiogorgonians and sponges can look nice in planted tanks. Groups of calm peaceful fish like Bangaii Cardinalfish, or yellow headed Jawfish, or provided that circulation is not too strong seahorses, can be a perfect fit for a graceful saltwater plant aquarium.

Placement: Some green plants like Sea Grasses, Shaving Brush, and Mermaids Fan grow in very shallow water and should be in bright direct light, give them as much light as you can, ten watts per gallon would be good for such plants when possible. Place other green plants where they get plenty of light at least 4 watts per gallon or what you would give a typical coral. Appears that red algae plants need less light and can be placed lower in the tank but being from deeper water red plants can in fact utilize blue light like corals.
For tanks with large snails, sea urchins, and herbivore fish you may want to place plants in a refugium.

Gas Exchange
In a heavily planted saltwater tank it is recommend that you install an air stone or bubble wand. It should be plugged into a simple fish tank air pump and a standard electrical timer so it comes on when the lights go out. This can be very important to your plants but more important to your fish and other animals, because at night when the lights go out photosynthesis goes in reverse. When the lights are off the plants will stop producing oxygen, instead they will consume oxygen and they will start producing carbon dioxide. Thus oxygen levels will drop substantially. The air stone will remove carbon dioxide by displacement, and will replace it with room air containing fresh oxygen.

FINAL IMPORTANT TIP
As stated above please do not keep sea urchins, plant eating fish, large snails like turbo snails, or other herbivores with marine plants. They will rapidly consume them.
Plants can be kept in a refugium or well lit sump filter if your tank already houses herbivores.

For more invertebrate choices see:

Starfish
Lobsters and Shrimp
Crabs
Snails
Clams
Giant Clams
Sponges
Saltwater Aquarium Plants
Clean up Crew Packages
Or Click Here For General Information On Invertebrates.