What is a mangrove?
Mangroves trees that grow in coastal regions in tropical geographies. In the U.S., I think of Florida as being the haven for mangroves, although there are mangrove forests covering more than 50,000 square miles, across 118 countries.
A dense grouping of mangroves is called a mangrove forest, where the trees grow along the edge of the water, packed closely together. The iconic view of a mangrove forest displays the prominent root structure, as the trees extend their roots into the saltwater.
That’s right, saltwater. Mangroves don’t require saltwater to thrive, but rather they are salt tolerant, which means they can grow in freshwater, brackish or saltwater. Mangroves have adapted to life along the coast by filtering out the salt from saltwater and excreting it out through their leaves.
In the wild, the roots from a mangrove forest serve as a nursery for juvenile fish, which can be seen swimming among the roots.
Why mangroves in a reef tank?
While there are some practical benefits of keeping mangroves with your saltwater aquarium, which I will get into in a moment, probably the most important reason to keep these cool trees is because you like the look of it.
A Natural and Living Structure for your Fish
Mangroves grow in tropical regions and act as a nursery for juvenile fish. The tangled network of roots, extending down through the water and into the sediment create a natural structure for the fish and provide protection from much larger predators. In the reef or lagoon aquarium, this can provide you with a natural living structure for your fish, to supplement the live rock in your display.
Another reason to keep mangroves in an aquarium is for nutrient export. Mangroves, like the algae you would keep in a refugium, will help purify your aquarium water by removing some of the natural waste products produced by the animals in your tank that would otherwise foul the water and fuel problem algae outbreaks.
What kind of maintenance and care is required?
If you have a shallow tank, consider planting your mangrove propagules (the thin green shoots) directly in the soil.
If you have a larger tank and want to try to recreate the look created by the tangled, knobby roots, suspend the mangrove propagule in the water column so that the base is submerged, while the rest of the shoot extends out of the water. The roots should grow down and work their way down into the substrate.
Mangroves are trees. They require light for photosynthesis. If your room has strong light from nearby windows, that may be sufficient, otherwise you will need to house them under the aquarium lights for your display tank or refugium.
Mangroves roots will grow in the saltwater of your tank. As long as the roots are submerged in the saltwater, they should not require additional watering, with one exception (below).
The way mangroves ‘cope’ with the salt in saltwater is that they export the salt out through their leaves. According to an article in reefkeeping magazine, it is advised that you clean the accumulated salt off of the leaves of the mangrove tree a few times each week by spraying the leaves with fresh water (assuming it is safe to do so…and that you don’t have electrical equipment in the vicinity).
Starting the journey
I just started the journey of keeping mangroves in my reef tank. I can’t wait to share my progress (and mistakes) with you here.
The roots emerged from the first propagule ~9 days after bringing them home. There are no roots on the second, smaller shoot. In hindsight, that’s not all that surprising. I suspect the larger propagule is healthier overall and may prove to be a faster grower. Neither propagule has demonstrated any leaf or branch growth yet.
For more information about mangroves in a reef tank, check out the resources below: