Using Mangroves in Saltwater Aquariums

How to use mangroves in saltwater aquariums

Mangrove seen partly underwater
Kim Taylor and Jane Burton / Getty Images

A number of years ago, some aquarists discovered that using mangrove plants in their saltwater aquariums produced a number of benefits. The biggest benefit was that the plants removed a lot of toxins, such as nitrates, phosphates, and DOCs from their aquarium water. In some cases, the DOC reduction was so great that they found a protein skimmer was no longer required as, once the mangroves were installed and began to grow, the skimmers stopped producing the gunky skim-mates that were being produced before.

There are several species of mangroves that are used by aquarists as a means of filtration, particularly to reduce DOCs, nitrates, phosphates and other toxins in a saltwater aquarium; White (Laguncularia racemosa), Oriental (Bruguiera gymnorrhiza), and Red (Rhizophora mangle L.).

Mangroves possess a number of unique "oddities" in the flora world which make them adaptable to many environments. Mangroves are plants that live in freshwater swamps and along brackish and saltwater shoreline areas. They have the ability to live in saltwater by straining freshwater from the saltwater through their roots. The cells in the roots take in water, but because the root cell pores are so small, they do not allow the salt molecules to be absorbed. Nature's own little RO/DI unit.

Introduction of mangroves to an aquarium is normally done by way of the seeds, which look like long pods that are fat at the bottom (root area) and skinny at the top (leaf growing area).

Newly produced and shedded seeds float around on top of the water, drifting with the tides and currents until they finally come to roost. The seeds only need a short period of non-movement to start anchoring into the mud, sand, or rock structures they often get trapped in between.

There are four basic stages of mangrove seed growth that one can buy.

Mangrove Buying Tips

Some suppliers cultivate and harvest mangroves from the wild, while others aquaculture them in closed systems. If buying over the Internet, check your local laws. There are some U.S. states and undoubtedly other countries that prohibit the importation of mangroves. If you live in or are traveling to an area where mangroves are endemic and you wish to collect your own, once again make sure that you check the local laws first. Some U.S. states, like Florida, consider the mangrove to be a "protected species", with hefty fines incurred if you are caught with them, while others, like Hawaii, consider them to be a "weed", having little or no concern about anyone collecting or having them.

There are four basic stages of mangrove seed growth:

  • The seed with no roots or leaves.
  • The seed with knobby root starts beginning to form, but no root sprouts yet.
  • The seed with some roots started and a leaf sprout formed.
  • The seed with a full root system and fully grown leaves.

If you get seeds in the first or second stages, it will take a while for them to mature. Mangroves in the third stage have a good root start and will grow to maturity faster. In the fourth stage, you already have mangroves with an advanced root system, and you can generally see results in a very short period of time after introduction into the aquarium.

Mangroves range in price anywhere from about $4.00 up to $25.00, usually based on the stage of seed you purchase and how they were grown. Check with your LFS to see if they have mangrove plants available, or purchase them online.

Just remember, if you are going to buy mangroves you need to know how to acclimate them before you get them.

How to Acclimate Mangroves

The biggest mistake that one can make is to immediately slam the mangroves into some water, expose them to intense lightings, such as metal halides, and then hope for the best. This is a sure-fire course to failure.

Mangrove plants received by mail order will more than likely have been in transit for several days without light, water, and CO2. The plants can literally be in "shock" when you open the package. Therefore, they should be slowly and carefully acclimated and introduced to their new environment.

After shipping, sometimes they may even go through a dormant stage, but if cared for properly they will awaken from this dormant stage and continue to grow and mature.

Hopefully, the plants you receive will have been well prepared for shipping. To us, this is best done when the leaves and roots are wrapped in a damp water absorbent material (paper towels/newspaper) and sealed in a plastic bag. Remove the plants from the shipping material and gently rinse them in room temperature fresh or tank water. This will remove any extraneous contaminants, and allows the plants to "breathe" and adapt them to their surroundings, before placing them into their new home.  

Mangrove Placement & Care

The method most often used for keeping mangroves is to place them in a sump, or a refugium can be used. The seeds are inserted into pieces of styrofoam and floated with the roots in the water, then provided with a plant light source, and some aquarists suggest an iron supplement.

Since we didn't have a sump or a refugium, we always placed our red mangrove (Rhizophora mangle L.) plants directly into our aquarium by submersing the root systems in the tank water, after they were precleaned and acclimated, and kept the leaves above the tank lights. We found that exposure to less light for the first few days/week was better. In fact, they grew quite well just from the ambient tank lighting and we never had to add a separate plant light, nor did we ever add an iron supplement.

If you are concerned that your plants may not be getting the light they need, add or increase the lighting gradually. A 40-watt plant light will be sufficient. Don't place the light too close to the plants, as this can fry the leaves. As a test, put your hand between the light source and the tips of the leaves. If you can feel the heat, the light is too close!