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View, A Guide to the Ecology and Care of Mangroves
by Julian Sprung PDF. Opens in a new window for your viewing pleasure.
What is the advantage of having mangroves in a reef tank?
Mangroves take the nutrients necessary for their growth from cloudy aquarium water, the term cloudy aquarium water here is meaning "nutrient rich water". This means that we have a means of exporting phosphates and nitrates. Macro algae do the same, but they easily set those nutrients free when they are eaten by fish or die and dissolve. With mangroves this is different, at least if the aquarist succeeds in preventing the mangrove leaves from falling into the water and dissolving there. While many mangrove species export excess salt by depositing it on the surface of their leaves for the rain to wash away, some mangrove species deposit excess salt inside of their oldest leaves, which then will turn yellow and drop down. This is a natural process, but in the reef tank we just have to make sure that the leaves will not dissolve in the aquarium water and release nutrients back into the aquarium water.
But, on the other hand, regarding the nutrient export capacity of some mangrove plants living on the upper zone of our reef tank, we should not expect high levels of aquarium filtration right way; rather it's a gradual process. They are slow-growing plants, and their nutrient uptake is limited. To say it clearly: if we have the problem of exporting phosphates and/or nitrates from our tank, due to over-feeding fish food, insufficient foam fractionation, etc, we will certainly not be able to solve it by planting mangroves. Having mangroves in the tank just helps to make the man-made biotope a little more natural, in function and appearance. If we try to create something we call a "mini reef," we should take every opportunity to employ natural mechanisms. Even though their functional contribution to the system is relatively small, it makes our "mini reef" a bit more natural.
For which types of reef tanks are mangroves suitable?
Of course, a tank where we want to plant mangroves needs to be open on the top and free of other
fish aquarium supplies, so the plants have space to grow. Theoretically, we can also cut an opening into the light hood of a closed tank, but from an aesthetically point of view this can hardly be satisfying, at least if one tries to copy a natural beach area. The most fascinating thing with mangroves in a reef tank is - at least to my opinion - the view from the top in front of the tank on the little "coral reef" that extends from the "deep ocean" to the "shallow lagoonal area," ending in the mangrove-populated "coastal zone." With a light hood this does not work.
Another type of tank for mangroves is a special mangrove-aquarium. This can even be done with a
How do you plant a mangrove in a fish tank?
filter fish tank and is very simple. Julian Sprung has a tank of this type connected to his "famous" little reef tank. All you have to do is to take a few mangroves that root on some porous lime rocks, place it in the center of this tank and surround it with some corals typical of the lagoonal zone. A weak water current is sufficient for the mangroves (but obviously you should also ask the corals for their opinion). This mangrove tank can be connected to your main marine fish tank, for example by placing it a little higher and pumping a small amount of water from the reef tank into the mangrove tank, so it will flow back into the reef tank via gravity. With the help of a timer you can even add a second pump which will pump at certain intervals and transport more water into the mangrove tank, resulting in a higher water level. By doing so you will imitate the natural high and ebb tides. If you create the decoration of your mangrove tank in a way that lets some areas fall dry during ebb tide, you can even add animal life typical for this mangrove zone, a fascinating thing.
Under natural conditions, mangroves do not only root in mud, but also in lime rock aka live rock. Consequently, we can offer them some porous lime rocks placed in the upper area of the tank. The simplest way is if you push the propagules between two or three porous rocks, allowing their roots to grow into the pores. If the propagule already has developed fine roots when you get it, you can also lay those roots around a porous lime rock and carefully fix it with a rubber band, waiting for the roots to hold tightly to the rock This way it is easy to change the plants location at a later time, though this should be avoided as far as possible because the plants strongly adjust to their environment, especially to the illumination.
But a single mangrove has little similarity to a mangrove forest. If you want to have a "real mangrove forest," you may need to employ a different way of fixing the plant in the water. For this purpose, I have embedded the propagules into rock wool and placed the whole thing in a small grid basket formed of plastic commonly used for freshwater aquarium plants. The roots grow through the rock wool and the holes in the basket, holding the plant tight. This basket makes it easy to connect several mangroves to each other by using nylon cable ties. That way I have created groups of mangroves that stabilize each other in their position.
If you want to create a "beach zone" with fine white sand and mangroves on top of your tank, you can go one step further and connect those plastic baskets to a perforated plastic sheet (PVC or acrylic). This sheet with mangroves then gets placed in the upper area of your tank, where you can cover it with coral sand, coarse grain size on the bottom of the sheet, and covered with fine white coral sand.
The simplest illumination for the mangroves is the light emitted at the side of a halide lamp. But you need to make sure that the plants don't grow directly under the lamps because of the strong heat emitted there. Also, the plants would shade corals when growing directly under the lamps. The stronger your halide lamp, the greater the distance you need to plant the mangrove from it. But, if necessary, you can cut the plant in shape at a later time when it grows branches too near to the lamp. Also the color temperature of the lamps is of importance for the mangroves. The best light for mangroves is, of course, a daylight lamp at 6,000 Kelvin, since they are land plants. With a lamp of 10,000 Kelvin it may also be possible to grow mangroves, but a 20,000 Kelvin lamp will probably make it harder to satisfy the physiological needs of mangrove plants (though I have not tried it).
Mangroves and daylight
If the aquarium is placed under a window, we can also use the natural daylight to grow mangroves. In this case, we can even illuminate the tank with fluorescent tube lamps, even with a closed lamp hood having a hole for the mangrove. An alternative to the natural daylight or the halide lamp would be a special plant lamp hanging on top of the mangrove. That helps placing the lamp a greater distance from the mangrove, and also permits putting it right on top of the plant, resulting in a more natural looking growth form. Note: If placing the aquarium near a window which receives plenty of natural sunlight to accommodate your mangrove, make sure to take the necessary measures such as employing a chiller to keep the aquarium water at proper temperatures.
Maintaining mangrove plants
Mangrove plants don't need much care; care can easily be given while doing your regular
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fish tank maintenance. The most frequently traded mangroves are Rhizophora mangle, which exports salt by producing a thin layer of salt crystals on top of their leaves. This should be washed away daily - or at least two to three times per week - by spraying fresh water on top of the mangroves. We use distilled water for this purpose. Be very careful when spraying water on to the mangroves on top of the aquarium if there are lamps and electrical outlets! That is about all you have to do other than cutting some branches occasionally or even the growth tip of the plant if it comes too near to the lamp.
by Daniel Knop
Sprung, J. (1998): Herrliche mangroven. Aquaristik aktuell 3/4 1988, Dahne Verlag, Ettlingen
Storch, V. & Welsch, U. (1997): Systematische Zoologie, 5. printing. Gustav Fischer-Verlag, Stuttgart
Knop, D. (2001): mangroven im naturlichen Lebensraum. KORALLE 9, June 2001
Knop, D. (2001): mangroven im Riffaquarium. KORALLE 10, August 2001