Special Mangroves

Special Mangroves


Mangrove is a generic term that refers to that vegetal (or forest) formation made up of predominantly woody plants that grow on the low coasts of tropical sea coasts, particularly in the band periodically submerged by the tide.

The dominant species of the mangrove forests are around fifty, but which are resistant to marine salinity are only the Rhizophora mangle (red mangrove) and the Avicennia marina (black mangrove), which can occasionally be found on the market.

The two mangroves look very different. Raising young mangroves in a marine aquarium can bring excellent advantages in managing the tank, but this only happens if the plant is well and healthy. Very often those who have tried to cultivate them say that they have slow growth and find it difficult to live, without having noticed substantial differences in the water values. This may be true in our tanks because we don’t treat it decently.

The mangrove in nature is a tree many meters high on which entire ecosystems are based in various parts of the world, why is it slow and difficult to grow in our aquariums? The common attitude is the following: if an SPS coral doesn’t grow it’s the fault of the aquarist who is doing something wrong, if the mangrove doesn’t grow it’s the fault of the mangrove.

Fifty years ago someone probably said that the SPS were unfit to live in captivity due to their delicacy, the truth is that the method followed 50 years ago was very different from the modern Berliner. With this attitude you don’t get very far, you adapt to the limits imposed by hearsay, but there are always more open-minded people who study and experiment, and invent systems such as DSB, zeovit and Berlinese.
Even the natural method arrived after more complex management with sand filters.

To end this little critique of aquarium keeping, I often read opinions about certain animals such as Lima sabra, Fromia, Crinoids, tunicates and others which are considered unsuitable for breeding, their purchase is not recommended and it is said that they are difficult animals slowly starving. The truth is that it is the methods used to manage the tanks that are not suitable for those animals, not the other way around, as some peacefully like to tell themselves.

I personally was very fascinated by the positive experience that some people have had with Miracle Mud, telling of miraculous healings even on crinoids
( http://www.zanclus.it/pagine/az_miracle_mud_agg.php).

The neophyte is taught to decide first what he wants to breed and then to equip the tank with lights and all, yet many times I have heard criticism of the MM from people who have not had very good results on some animals, but these people have never been successful with a crinoid using the zeovit method?

Perhaps the Zeovit method is the best for those who want to breed SPS, but the MM could be the best for those who want to breed beautiful and less common organisms such as crinoids, tunicates and filter feeders in general… a good aquarist should improve/modify the method, not demolish it first. But the SPS are noble and worthy of a thousand respects, the crinoids are “unsuitable” … like the mangroves

Returning to the main point, the greater growth success of the Caulerpa compared to the mangrove is not in the organism itself, but in how it is raised. Caulerpa grows fast because it is treated for what it is: algae. If the mangrove were treated for what it is, a tree that tolerates salt water, it would give excellent results, instead, it is treated like algae.

Before speaking of plant physiology we saw the ability to absorb nutrients that a “real” plant has and therefore we understand its filtering power in our tanks, for this reason, those who have treated their mangrove well report miraculous filtering effects, of

there hadn’t been these results no one would talk about mangroves in the aquarium for years now.

The mangrove would like:

  • – mineral salts (it takes them from the water and the bottom substrate)
  • – light, the more there is, the better.
  • – temperature around 26 degrees all year round (but it resists much less)
  • – preferably brackish, freshwater, and even if it is a nuisance it can be adapted to seawater.

Let’s examine how it is treated in the aquarium:


This parameter is the only one that is always well respected in the aquarium because it matches the needs of the other guests.


In most cases, mangrove seeds or freshly germinated plants are sold to aquarists. As silly as it may seem, a seed is not an adult plant. No one expects a Zebrasoma fry to clean the tank of algae but everyone expects a seed to filter 100 litres of water… if you asked questions, they would answer themselves… The thing you must always remember with mangroves (or anything else related to the aquarium) is patience. The results will only be there after a couple of months, but they will be there.

How many mangroves are needed to achieve the desired effect? Different authors recommend different numbers, usually one seed is recommended for every 10 -20 litres of water. Young trees can be used in large numbers. But later, when they get bigger, you have to remove them, otherwise, they won’t have enough organic material.

But as explained before I would not remove plants from the tank after the changes to the bacterial flora they have caused in the bottom. There is no fixed rule for the number of plants useful for filtration, it must be calculated that the mangroves compete with the skimmer, therefore more plants can be placed in tanks with the natural method, in tanks where the skimmer is not satisfactory (it happens often) the number of plants will be somewhere in between, in tanks where the skimmer is oversized and the water is very thin, the mangroves will have to be limited in number.


Very often the mangrove seeds are stuck in the tank, they come out to breathe only with the tip and for their growth they have 10 or 15 cm between the water and the burning lamps. Although it is obvious that this solution fails, it remains the most used.

Rhizophora is a tropical plant, as is the more common Ficus benjamin, if near the tank you have house plants (they are all tropical) that live peacefully, it means that the light present in the room is also suitable for the mangrove, remove the light from the sump and make it grow in height like the Ficus next to the house… um… in a pot, you will also save on electricity. You can also think of innovative types of sumps, perhaps a sump planter.

Instead of imagining the sump as the draft of your tank, think of it as a vase for hydroculture, or modify one of that beautiful ceramic pot covers that your wife really likes (for the Ficus), place it near the tank with the equipment inside, such as calcium reactor, the osmoregulator or whatever, from the vase, you will only see two pipes and the foliage of the mangrove, which doesn’t care about having its roots in the dark.

The tub will be attached to the sump planter just like a traditional tub would be. If you are puzzling over how to divide an inexpensive garden pot cover into compartments, the do-it-yourself geniuses will surely find valid solutions, but in my opinion, it is not necessary: ​​you put all the substrate for the mangrove in a traditional plant pot (new clean and disinfected) or a glass container and you put the seedlings in it, you immerse it in the pot cover full of seawater, you place the rest of the equipment all around it.

This solution is easily exchangeable for a houseplant, it could even be positioned at the same height as the tank with the possibility of having two birds with one stone: a wife who is not disgusted by the sump and live zooplankton entering the tank, nobody forbids doing hatch artemia or other between the roots of the mangrove.


The Rhizophora can live there but also for this plant, it is an extreme environment, they manage to germinate a much lower percentage of seeds than those that fall in an area wet by low tides, or in freshwater. Germinate the seeds in brackish water at 5 ppt (5 grams of salt per litre), and then gradually bring the salinity to reef levels before introducing everything into the tank circuit.

Salinity has a significant impact on the growth of Rhizophora. Red mangrove seedlings show the fastest growth rates in all plant tissues (leaves, stem, and roots) at 5 ppt salinity, grow least fast at zero ppt salinity, and at 20 ppt salinity the growth rate is strongly limited [17].

The salinity of our reef aquariums is around 35/36 ppt, therefore decidedly not optimal for the mangrove. The fact that at high salinity the mangrove is limited in growth does not mean that it grows slowly in general, but that it grows slower than those that live for example at the mouth of the river where the salinity is lower.

The mangrove however continues to grow and produce more dry matter than the algae. But it is an important fact because it makes us understand that even the Rhizophora is not a tank, the marine environment is extreme for it too and the plants that live there are more delicate than those that have had the good fortune to be born in brackish water.

Despite the salinity, the mangrove lives and thrives in our city reefs if the other conditions are good, but if it starts to lack light, or does not have enough N and P because there are too few in the tank, or gets cold in winter … then it no longer gives its miraculous filtering effects.

It is an organism that can be very useful in the ecology of the tank but one must not think that it is like a turbo snail that is thrown in and then gets by: one must keep up with the mangrove, one must observe it with the attention with which one looks at the tank because it is an integral part of the system. If it’s big, it could be “the system”.

If you are lucky enough to find a marine Avicennia on the market, it has a better tolerance than salinity: its growth peak is in fact at 15.4 psu [18] of salinity against the 5 ppt of Rizhophora mangle [17]. The measurement in ppt can be equated to the measurement in PSU (practical salinity units) because in the physics of fluids, they are “dimensionless ratios”: 5 ppt = 5 PSU = 5 grams of sea salt per litre = 5‰ [19]

Mineral salts:

Liebig’s law is clear: “it is enough that even a single microelement is missing to block the growth of a plant” (http://it.wikipedia.org/wiki/ Legge_di_Liebig). In the sea, the water is rich in nutrients and the Mangroves sink their roots in poor soil or even the beach, all in all, their thought is not to find the nutrients but how to extract them from the salt water.

Marine aquaria are often too poor in nutrients for a mangrove, not as regards N and P which are continuously produced by the fish and manually added by us with the food, but they are deficient in all microelements such as iron, manganese, iodine and many others. All these nutritional elements are in the water in the form of ions and bind to the “dissolved organic carbon” present in the tank, quickly ending up in the skimmer.

Each milligram of dissolved organic carbon has the ability to bind 1 micro equivalent of metal [15]. In this condition, the newborn Mangrove plant is already in nutritional deficiency: a plant that does not grow does not remove P and N from the tank. The second thing in aquariums mangrove trees are almost always suspended in mid-water… look around, how many trees do you see suspended in mid-air? Or grow without soil?

For mangroves, it is only possible to do this in tanks with high concentrations of nutrients but this is not the situation we would like. But which substrate to use? The sand of the DSBs is full of bacteria but not of mineral salts, but if you have at least 10 cm of sand you can have good results, you could sand the roots of the mangrove directly in the main tank provided that the ceiling light does not cover the whole surface but leave room for the plant to grow (it can happen on the edge of the tub).

But not everyone has a DSB so what other substrate to use? The land of geraniums is not good, that of the vegetable garden would make the mangrove happy but the corals would have to object… the Miracle Mud is the ideal solution because it satisfies mangroves and also corals.

It contains all the elements useful for plant growth and is non-toxic to guests. Someone associates the MM with the growth of algae because in the literature it is used in algae filters, but if they are not put there they do not grow by immaculate conception, above all if the mangrove devours all available N and P. Furthermore, the roots of the mangrove do not need light like the Caulerpa and the option of the sump planter mentioned above can be adopted.

What to do if the MM runs out? When managing tanks with the MM method, after 2 years it is recommended to disassemble the sump, remove 50% of the MM and put some back. Wow, what a concussion and what an imbalance in the tank! With the mangrove it’s simpler, pretend it’s your wife’s Ficus Benjamin when she transfers it because the earth is old, of course, she doesn’t remove 50% of the earth, she simply puts it in a little bigger jar.

It is not necessary to change the sump, just add another MM and raise its level slightly, the mangrove will have already emitted so many adventitious roots in mid-water… and starved the Caulerpa, and the sump does not need artificial lighting… that’s enough that of the window if the room is bright.

Reading about the MM I noticed positive comments on the health of corals including SPS such as airports, bright colours and miraculous healings… Liebig’s law is certainly valid also for zooxanthellae, probably also for corals.

Personally, I think so and I’ll explain why: corals have the same osmotic gradient as the water in which they live (hence the sensitivity to salinity) and having evolved in an environment with a uniform abundance of salts they have not provided for particular methods for their capture: they are absorbed by the cell membrane directly from the water.

Soft corals “also” absorb dissolved organic matter but “all” corals absorb microelements due to the osmoregulatory automatism typical of coelenterates. The SPS want very thin water, with this term we mean tanks lacking in dissolved organic matter, N and P… we necessarily supply it even thinner: deprived of the microelements which in nature are dissolved uniformly in all the oceans (salt purchased contains only a part, and also the skimmer eliminates many microelements)

Perhaps this is also why the MM method initially gives the tank a kick of life, and not just the presence of a little zooplankton. I would also add that the concentration of salts in the water remains constant: the MM releases to the water only the minerals that the plant has removed from the chemical-physical equilibrium following the precise laws which govern the solubility of metals.

Subtraction of magnesium and salts from the tank.

Mangroves are facultative halophytic plants, which means they can grow in fresh or brackish water and some species can tolerate very high salt concentrations. 

In the case of Rhizophora mangle and Avicennia marina, their success in marine environments is mainly due to the absence of competitors. All mangroves accumulate large amounts of salt in their bark, roots and leaves [20].

When the aquarist reads sentences like this he is frightened by the salt that the plant can remove and gets the wrong idea because in reality all scientific research when say that the concentration of salts in the plant is high they are comparing it with other plants earthlings who have never even seen salt.

Marine algae have evolved to stay at that density and are much richer if salted, while mangroves have only adapted to bear it and retain the physiology of terrestrial plants: the tolerance that their enzymes have towards salt water is very low in fact the sodium ion does not accumulate in the cytoplasm as in algae but in the vacuole where it remains more isolated. Mangroves have developed three strategies to remove salts from their tissues.

Although they live in an aquatic environment, they often have problems related to a lack of water because its intake must take place against an osmotic gradient, requiring a high expenditure of energy. Natural evolution has brought about adaptations that allow the plant to develop very negative osmotic potentials (minus 30/35 atm).

This allows the intake of water which is thus filtered so that almost pure water enters the plant. Only the amount of salt strictly necessary to produce these high potentials is introduced into the plant body and subsequently stored in the cell vacuoles of the leaves.

The excess salt is then eliminated by means of glands placed on the leaves which exude salt water (with a saline concentration of 41‰, therefore higher than that of seawater, but with the same relative concentration of sodium chloride and potassium chloride, respectively 90% and 4%).

It has also been shown that salt can be transported from young to older leaves. Furthermore, excess salt can be reduced by dropping the oldest leaves [20] [21].

But before all this happens, most mangroves can exclude 90 or 95% NaCl already at the root level. Specifically, Avicennia is better at expelling salt from the leaves (grains are visible on the underside, while Rhizophora is better at not absorbing it at the root level.

When a marine aquarist places a mangrove seed in the tank, she doesn’t think in the slightest that it suffers from dehydration… but it is a deeply felt problem for the seeds that have just been placed and the cause of many failures. In other cases, if the mangrove survives “the birth” and begins to grow luxuriantly, the inverse problem could arise: having to add osmosis water to the tank.

The third technique mangroves use to reduce salt toxicity is to reduce transpiration by accumulating water in the leaves because this accumulation of water dilutes excess ions. When you move a mangrove from fresh water to salt water, the leaves gradually thicken and become waxier (wax reduces transpiration), precisely because being juicier is a defence against salt.

But even in this case when the scientific literature says that they transpire less water from the leaves they are making a comparison with the average of terrestrial plants (also because no algae transpire water into the air), so for our hobby the amount of water “lost” it is still to be considered.

For terrestrial plants, the rule is that in full photosynthetic activity, a leaf transpires in 1 hour a quantity of water equal to its weight (the density of water is more or less negligible, therefore a litre of water is equivalent to a kilogram and 100 grams of water are equivalent to 0.10 litres or 100 centilitres).

If you have a 1-meter-high mangrove with 1 kg of leaves, “every hour” of sunshine throws 1 litre of water out of the tank. We know that the transpiring efficiency of mangroves varies according to salinity and other factors, but even assuming that they transpire half as much as the average of terrestrial plants, half a litre of water per hour which disappears from the tank is an important value, especially if added to the normal evaporation that we already have.

It’s funny how anyone cares about the micrograms of salt the mangrove has taken out! Having a healthy mangrove means adding osmosis water not salt… but since topping up is automatic and not done manually, the great geniuses of the aquarium hobby only noticed the infinitesimal percentages of salt because they are measured by hand, if the top-up tank is was empty it was the wife’s fault who kept the heaters too high in winter, or the new HQI lamps.

The transpiring capacity of the mangrove can be neglected in large tanks but not in small nano reefs with manual topping up … leave yourself 3 days and you will find salted anchovies instead of the nano reef, at which point the mangrove has eaten some of it will be your last worry.

On the internet I have seen very complicated procedures used to combat the nutrients in the tank such as adding sugar in the morning to stimulate the reproduction of bacteria and peroxide in the evening to kill them, at night the skimmer sucks them up eliminating nitrogen from the tank and in the morning it starts again. It probably works and I don’t doubt it but I see it as much more risky, complicated and expensive than having plants in the tank and adding salt to the changes.

Those who say that mangroves consume magnesium are saying something true, but this is partial information because research shows that their ability to absorb magnesium decreases with increasing salinity: in other words, they absorb more magnesium in freshwater than in salt water.


There are many plants that, being halophilous, live in environments with high salt concentrations. In Italy the pioneer plants par excellence are the prickly esparto Ammophila arenaria (syn. Ammophyla littoralis) and the radish Cakile maritima, but also the Salsola kali, and the Xanthietum italics.

Although these plants get very close to the seashore, they do not grow directly immersed in seawater, and no one has ever tested their use in the aquarium trade. Instead, an unknown plant in this hobby is much more interesting: Salicornia. Salicornia is a fruit of the Chenopodiaceae family (Amaranthaceae according to the APG classification), commonly spread on saline soils near ponds and coastal marshes.

In the intradural depressions of the flat beaches, there are halo-hygrophilous communities usually called glassworts. These are difficult environments, the conditions of which can vary greatly throughout the year, between the seasons and during the same day. After a period of drought due to intense evaporation, the brackish waters of these environments can even exceed 40‰ in terms of salinity, while after a sudden downpour, it can even drop to 10‰.

Furthermore, brackish environments are often in communication with the sea, even when it doesn’t appear to appear, so they are affected by tidal fluctuations. Various species of the genus Salicornia dominate vast expanses of mudflats that emerged during low tide, close to other higher plants.

These are low fleshy plants, glaucous green in colour (red in autumn), they have a bushy habit, forming a thickly and irregularly branched bush right from the base, and the branches are herbaceous and fleshy in the terminal portions.

Glasswort is even more interesting than mangrove due to its possible use as a filter in aquariums, in fact, compared to mangrove, it bears salt concentrations even higher than the marine one, while mangrove suffers from the strong osmotic gradient already at a salinity around 20‰.

Salicornia also has the advantage of not being a tree but of having dimensions and posture that are more manageable by the aquarist who wants to use it. Salicornia is not a tropical plant so it is much less demanding than a mangrove both in terms of light and temperature.

Salicornia is also relatively easy to find: for the more adventurous it also grows spontaneously on the Italian coasts, while for the less daring luck is on their side because it is a plant cultivated for food use, it is a typical Apulian product sold as sea asparagus, occasionally found in some supermarket packaged fresh and alive, obviously the one in oil is not good.

Salicornia shares the same physiology with the mangrove and with almost all halophilic plants, and therefore the same defence mechanisms against excess salt. Being an emerged plant it has all the advantages described above, and exactly how the mangrove affects the biology of the tank and the bottom in which its roots grow.

For those wishing to try the virtues of this plant as an alternative or in addition to the mangrove, consider that Salicornia is not suitable for inclusion in the main tank as only the roots grow submerged while the stems must remain in the air.

For those who have little space, being Salicornia a plant of modest dimensions and considering that it will often have to be pruned, it can also be inserted in special sumps inside the cabinet that supports the tank, using a layer of sand at least 7 or 10 cm high much less if MM, the seedlings are distributed in a thin layer between 2 and 5 cm of water.

There are many species all very similar and difficult to recognize, so you have no doubts if you have taken them from the wild and verified that they actually grow near seawater and are not one of the more inland species. 

The one sold for food is certainly suitable and multiplication by cuttings should not cause problems, but as in the case of mangroves it is advisable to cut or sow using a much lower salinity and then gradually bring it to reef level before placing it in the sump.

Salicornia fruticose is annual and therefore the plants live for a year, but if you reproduce them by cutting using the many twigs you prune to contain it, you will have new plants all year round. The seeds can be found for sale on the internet. 

Even if Arthrocnemum belongs to another genus, it is always a glasswort but has the advantage of being perennial and therefore only one plant lives for several years. Salicornia and Arthrocnemum are so similar that they are easily confused even by expert botanists, and are still considered variants of glasswort. On the internet, you will find a lot of useful information both by searching for one name and another.

Elizabeth Canales is fond of marine life since childhood and got an aquarium as a gift from her father on her 6th birthday. Since then she started to take care of Coralia (her goldfish). Her love for fish made receive her B.S. in Marine Biology from the University of Washington and DVM from Delaware State University.

Leave a Comment