The red mangrove tree, Rhizophora mangle, is a common sight around saltwater aquariums, reef tanks and local fish stores where fresh seed pods are sold and kept. What is not a common sight is for a mangrove tree to be doing especially well and growing because aquarists treat this noble plant like a piece of house ivy.
For some reason it has come into relatively common practice for saltwater aquarium keepers to purchase one or more mangrove seed pods but without any real attention to the care requirements. Most reefers simply place these pour souls in some random area of the aquarium with their leaves above the water, and not much else is given to their specific care requirements.
Let us break it to you, Mangroves are not like house ivy at all, and you can’t simply place a mangrove in your aquarium and hope that they do well. Mangrove trees are high energy living plants which need intense light, a proper growth medium, and frequent rinses of freshwater to do well in an aquarium, let alone grow.
To be clear, mangrove trees should probably never be placed right inside the aquarium, as most aquarium setups are designed to have bright lights placed directly above the tank, close to the water surface. Mangrove trees need to breathe so their leaves should emerge from well above the aquarium water.
If you truly want to keep mangrove, and want them to thrive, you should provide these high energy trees in an area of their own, where a dedicated light can offer them very strong illumination. In public displays the lighting for mangrove trees usually consists of very intense metal halide lighting, if not full exposure to sunlight, at least for part of the day.
Secondly, mangrove trees need to root down into a proper growth medium from which to obtain necessary nutrients required for growth. The substrate you use to grow and plant a mangrove tree should be deep enough for the tree roots to support a nice tree, but it shouldn’t be so fine as to cause anoxic regions to develop due to the absence of oxygen.
Finally and most importantly, mangrove trees require a regular rinsing of freshwater to wash away the salt from the surface of their leaves. The primary reason that mangrove trees can survive in saltwater at all is because they have special glands in their leaves that help to extract salt.
This extracted salt builds up on the surface on mangrove tree leaves, and in nature, a regular sea mist or rainfall would generally remove this salty build up. The regular rinsing of mangrove tree leaves cannot be overstated, especially in healthy growing trees that are given the intense lighting that they need.
The inspiration for this write up came from a visit we made to the Birch Aquarium at the Scripps Institute of Oceanography in San Diego. Behind the scenes we saw one of the most beautiful groves of Rhizophora mangrove trees which were being tended to while we were there.
The mangroves at the Birch Aquarium were given the white green thumb treatment with a dedicated ‘deep sand’ section in which the trees could truly grow their roots, and they were illuminated using a 1000 watt metal halide lamp. In addition to receiving regular misting with fresh water to rinse of the salt from the leaves, a sprinkler system is installed to further rinse the leaves during days in which a staffer is unavailable to do so manually.
Mangroves are majestic TREES that have been relegated to an aquarium ornament in most home aquarium setups. If you truly want to keep and grow a mangrove as part of your home aquarium, please give them what they need to thrive and you will be rewarded with a dynamic and interesting new dimension to your aquarium display.