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Marine Plants in the Refugium

What are marine plants?

Marine plants (flowering plants) unlike algae, have true roots, stems, and leaves containing vascular tissues just like terrestrial plants. There are approximately 50 known species worldwide and provide life and shelter to almost every marine organism. The most widely spread and abundant plant is Thalassia Testudinum, or turtle grass. In the aquarium trade there are five species that are available to hobbyists through various dealers and include: turtle grass, shoal grass, manatee grass, star grass and paddle grass. Although not as popular an addition to refugiums as macroalgae, sea grasses can be a beneficial and beautiful addition to any system. The most critical factor is the depth of the sand bed needed to grow and culture them ranging from 4-6 inches deep. Strong lighting is also essential to a healthy, thriving sea grass dominated refugium. 

Availablity

All sea grasses are protected by law in Florida and the Caribbean from direct harvesting unless by special permit. This often makes it difficult to find quality specimens because they have to be collected free floating in private lands or imported from other countries. Because of violent storms, dredging and commercial and recreational boaters, turtle, shoal and manatee grass are easily found as seaweed wrack washes ashore. The Halophia species however grow in largely protected areas such as the Indian River Lagoon and can it be difficult to find good specimens.

Turtle Grass

Turtle grass is the most abundant marine plant in the Caribbean and Gulf of Mexico. This particular plant has true flowers and produces seeds. Well established specimens have been known to flower in refugiums given the proper care. A slow grower, turtle grass will begin to replenish leaves gradually when given the opportunity to root itself in a suitable substrate. Care must be taken when planting new specimens as the root system is very sensitive and any damage could take months to heal. Like macroalgae turtle grass will take up many nutrients from the substrate but at a much slower rate. Overall it is a good choice for well equipped refugiums and will not cause harm to tank inhabitants. 

Manatee Grass

Manatee grass is the second most abundant sea grass in Florida. It is unique for having cylindrical leaves. The length of the leaves is highly variable, but it can reach lengths of 20 inches in deeper water. Manatee grass has been known to withstand salinities as low as 20 ppt. This sea grass has an extensive root system so a deep sand bed in necessary. It is found growing within turtle grass beds and is found in deeper water than shoal grass. A good choice as a refugium plant and once established will do well in most systems.

Shoal Grass

This particular sea grass is relatively small compared to the others, has thin flat blades and grows as a compact plant. Shoal grass is an extremely important sea grass because it grows in disturbed areas where turtle grass and manatee grass cannot grow. It is often found in waters too shallow or too deep for other sea grasses to grow. Of all the sea grasses shoal grass can withstand the widest range of temperatures and salinities. It is an excellent choice for refugiums because of it's shallow root system and smaller blades.

Star Grass

Star grass is in the Halophila family and can grow in depths of 30 meters. It is easily identified by a cluster of 4 to 8 oblong leaves.  Not much is known about this particular sea grass and it's rarely available in the aquarium trade, but is found from time to time. Prefers shallow water lagoons and mud bottom bays. A interesting specimen for the refugium if you can find it.

Paddle Grass

Paddle grass is also in the Halophila family and often grows as deep as 30 meters. It is a small bright green grass with a thin stem protruding into two distinct paddle shaped leaves. A very beautiful specimen that is limited in it's abundance but is available occasionally. A good choice for the refugium because it is smaller and doesn't require a very deep sand bed.