Month: July 2021

All marine plants are photosynthetic organisms and require a specific spectrum of sunlight to survive. Without the proper lighting, photosynthesis will be impaired and the algae and or plants will slowly die. The conditions that marine algae are subjected to in captivity are very different from those found in their natural environment. A typical aquarium is both nutrient and light deficient so marine plants must adapt to live under these artificial conditions. Without question, the use of some form of natural sunlight is the best way to grow marine algae and plants in an aquarium, but for most aquarists this is not an easy arrangement. Thankfully there are many capable artificial lighting systems that can achieve a similar spectrum necessary for photosynthesis. Most basic aquariums today feature a single full spectrum fluorescent bulb, but although it will illuminate the tank inhabitants, it is grossly insufficient to grow much of anything unless the tank is very shallow. Providing the proper lighting is an area that many hobbyists fail with respect to growing marine plants. Instead of providing a lesson on how plants and algae convert light to energy, we will focus on the proper spectrum and intensity needed for successfully growing marine plants in the aquarium.

Light spectrum ratings are identified by the Kelvin temperature scale.  The lower end of the Kelvin temperature range bulbs are most suitable for growing marine plants and are typically available in the 5000K – 6500K range. If your aquarium will include soft corals, most marine plants will also grow quite well under 10,000K lighting. This is normally a more pleasing spectrum to the eye, as the lower temperature bulbs can appear green or yellow. Unlike terrestrial plants which grow above the water or submerged at shallow depths, macro algae grow in different spectrums of light depending on the depth and species. Depending on the intensity and kelvin temperature the changes in color among different species can be quite dramatic. There are a few varieties of red macro algae for instance, that can be found in shades of red, yellow and brown within the same species. The distinct coloration is caused by the pigments associated which each species and the spectrum of available light it receives. Overall most macro algae and sea grass will do well under full spectrum lighting. The exception is with some varieties of red macro algae, which prefer a much bluer spectrum and can benefit from some supplemental actinic spectrums. Mixing color temperatures is preferred and is the most appealing while still allowing for optimum growth. Too much red spectrum can fuel the growth of less desirable algae both on the macroalgae and in the substrate.

The same principles that apply to freshwater planted systems and some soft coral dominated aquariums translate to the marine planted aquarium and/or refugium. As a general rule, most marine plants and algae need roughly 3-4 watts per gallon of full spectrum lighting to grow. Of course, this is an older style formula that has certain limitations and must be adjusted to allow for very small aquariums or those that are deep. Also, if using a high output fixture (vho, metal halide, led floods), less watts per gallon are generally needed and the par value is much more accurate when determining how much intensity is actually needed to penetrate the water column. A few deep water species can do well in low light conditions, but will grow much slower in this environment. Sea grass however, need large amounts of intense full spectrum light.

The most common types of fixtures available to light a refugium or marine planted aquarium include fluorescent, metal halide and led fixtures. The brightest but least energy efficient are the metal halide fixtures and the least bright and or efficient include standard output florescent fixtures.

Fluorescent Tubes

Fluorescent lighting is an older, less efficient way to light an aquarium and most modern manufactured aquarium lights are now powered with leds. High output florescent fixtures are still popular with some hobbyists because of their excellent kelvin and par ratings, but have a higher operational cost due to the short lifespan of the bulbs and the amount of energy required to power the ballasts. The high output bulbs include very high output (VHO) and high output (T-5 HO). VHO lighting is an excellent fixture for growing marine plants, but has been replaced by the popularity of a newer technology, the T-5 high output fixture. Similar in intensity to the power compacts, the advantage of the T-5 is that the amount of light is spread more evenly over the aquarium. They are also more economical and take up far less space than traditional T-12 and T-8 bulbs. In general high output florescent fixtures are completely adequate to grow almost any species of marine macroalgae.

LED (light emitting diodes)

Led light fixtures have come a long way since their introduction into the aquarium hobby more than two decades ago. They’re the most efficient fixtures, using about 70% less energy than a typical metal halide fixture. Because they are not actually bulbs, they require a lot less power to run as well as much less heat. The fixtures can be mounted closer to the surface of the water so they also are better at penetrating deep tanks. In addition to being very energy efficient many fixtures have fully programable spectrums and intensities. The flood style led fixtures offer the most intensity and highest par values for lighting a marine planted aquarium. The most efficient light fixtures have a high CRI (color rendition index) or PAR (photosynthetic active radiation) value and offer the hobbyist the most beneficial light available to marine plants. Again the best kelvin temps are in the 5K to 6500K range. Although they’re a modern and economical choice for aquarium lighting, leds don’t last forever and eventually the phosphorus coating will start to disintegrate changing the color spectrum altogether. Although sufficient for many species of macroalgae, some species don’t grow as well under available led spectrums.

Metal Halide

Metal halide lighting is the best lighting method for the reef aquarium to date. Even with all of the innovative technology in modern led lighting it’s unlikely they will ever replicate the spectrum quality and intensity of metal halide bulbs. The problem with metal halides is that they require an excessive amount of wattage to power even a small 100w fixture and produce a lot of heat when operated. The bulbs must be replaced every 6mos to a year as they lose their effectiveness over time. For this reason, they have largely been replaced with more energy efficient fixtures such as leds. Some hobbyists still use them despite the drawbacks, so if you can stomach the high operational costs it’s an excellent choice for a marine planted aquarium.

In the marine aquarium there are three main types of filtration that are essential to a clean and stable environment. They are mechanical, biological and chemical. There are many commercially available products that combine these in one unit, such as canister filters, power filters and trickle filters but most are not suitable for a marine planted aquarium. Many of these designs will become nutrient sinks in time and can release large amounts of nitrates and phosphates into the aquarium water. While flow-through filters may be beneficial for some heavily planted aquariums and even necessary, generally it will create conditions favorable for excessive, undesired micro algae growth without regular cleaning of filter material. Maintaining an aquarium with marine macro algae and plants is often a balancing act between controlling the buildup of nitrates and organic material and providing just enough for a healthy ecosystem.

Mechanical Filtration

For the marine planted aquarium the use of some form of mechanical filtration is normally needed. Plant material in time will break down to form sediments that can become nutrient sinks over time, especially in smaller aquariums. Some of this organic material will break down and be consumed by both macro algae and sea grasses but will also encourage micro algae growth. Depending on the size of the system these include the use of foam filter pads, micron filters and sock filters. Filter material should be cleaned or replaced often as they get dirty quickly in marine plant dominated systems. Protein Skimmers are very efficient at removing organic material and can be used in large systems that have a substantial bio-load. Some models are better than others, but most available today will produce good results. Over skimming can remove beneficial organisms, so running a skimmer continuously in a marine planted tank is not desirable as it will remove too many nutrients that the plants need to grow.

Biological Filtration

The best form of biological filtration for any marine system is the use of live rock or coral rubble. Live rock is full of organisms and bacteria that naturally filter aquarium water by consuming and converting nutrients and breaking down harmful elements through denitrification. Live rock is natural, attractive and provides a surface for marine plants to anchor and thrive. Uncured live rock is the best choice if it is cured properly because it will contain much more life than cured live rock. Aqua cultured live rock, although sometimes more dense than wildly collected rock, offers the hobbyist with the most variety of marine life, including beneficial bacteria, invertebrates and macro algae. External or internal pumps provide water circulation which is important for live rock to function. The size of the system and its inhabitants will dictate how much flow is ultimately needed.

Chemical Filtration

There are three main types of chemical media that are used to filter aquarium water. They are activated carbon, phosphate absorbing, and nitrate absorbing media. The use of activated carbon to chemically filter aquarium water has long been the preferred choice in both fresh and salt water aquariums. Although it can be useful in a marine planted aquarium, carbon should be used sparingly as it also can remove needed compounds and nutrients from the aquarium water. Phosphate and nitrate removing media can be used when levels get out of control but should be removed at the recommended interval so that the nutrients do not leach back into the aquarium after they have out lived their ability to absorb nutrients. A deep sand bed can also be utilized in a planted tank to control the amount of nitrate through the formation of anaerobic bacteria deep within the sand bed. Most deep sand beds need to be 6″ or so to be effective however as too little depth can create a toxic mess. Overall nitrate is needed by all marine plants and depending on the rate of growth its presence in low levels is beneficial to the health of the system.

Water Quality

Aquarium water for use with a marine aquarium is made by dissolving salt mix with either purified water or tap water. The composition of household tap water varies greatly depending on what region the hobbyist resides. Tap water can be hard or soft, alkaline or acidic and contain variable amounts of other elements. Most salt mixes in the industry are composed of all naturally occurring elements found in natural seawater. Purified water is the best choice for any marine system as it removes 99% of contaminants and nutrients from the water. Sources of purified water include demineralized, reverse osmosis/deionization, and distilled water. In some cases tap water can be treated chemically and used in a marine planted aquarium. This is done with large scale aquaculture as the excess nutrients are quickly consumed by the plants. For most aquariums, purified water is the best choice and will help to drastically reduce unwanted algae blooms and harmful elements. If you live near the ocean, natural seawater can  be used, but can often add unwanted bacteria, pathogens and free floating algae to an aquarium if not treated. This can cause problems long term. Water changes are very important when maintaining a marine planted aquarium and help to remove nutrient rich water and replenish elements lost that were absorbed by the plants. The buildup of sediment on several species of macro algae such as Botryocladia can be avoided by regular water changes, increased flow and mechanical filtration methods.

PH

Natural seawater has a PH of 8.4. While most marine plants and organisms can survive in a wide range, it is best to strive to maintain a level as close as possible to natural conditions. An elevated ph can help reduce the growth of certain micro algae as many prefer a more acidic environment. 

Alkalinity

Alkalinity is the measurement of water’s ability to neutralize acids. The alkalinity of sea water keeps ph stable and a drop in alkalinity will lead to an eventual drop in ph. Most aragonite sand and salt mixes are sufficient to properly buffer aquarium water containing primarily marine plants. Again, water changes are essential for optimal health in any marine aquarium.

Temperature

Most tropical species of marine plants can survive in a wide range of temperatures from about 72 degrees to 86 degrees. Some species found in both tropical and sub tropical environments grow in seasons however and have a distinct preference for certain water temperatures. The green macro algae Ulva is one such algae that prefers cooler water temperatures and will not survive long in any aquarium above 80 degrees. Sea grasses begin a dormant stage when the water temperatures are in the low to mid 60’s and although remain alive, they will not grow. In the marine aquarium a range of 76 to 80 degrees is acceptable and should not present any problems for most tropical and sub tropical macro algae and sea grasses.

Specific Gravity

Slight differences in salinity or specific gravity has no negative effect on the photosynthesis and growth of marine  plants. Many varieties of sea grass can adapt to very large swings in salinity in their natural environment. The change however, must be gradual, as a drastic change in salinity can cause most marine macro algae to undergo the process known as sporulation. When adding fresh water to an aquarium containing marine plants, especially Caulerpa, be careful not to change the overall salinity of the tank too quickly. Specific gravity levels in a marine aquarium are normally 1.024 – 1.026, but marine plants can survive in slightly higher ranges if desired.

Water Circulation

The ocean is a dynamic and constantly changing environment, currents, tides and storms produce enormous amounts of exposure to plants, coral and fish. Water movement is very important for the growth of all marine plants in the aquarium. It aids in the removal of sediment, prevents some epithetic growth and provides increased diffusion of nutrients. Species such as Halymenia greatly benefit from strong flow to maintain their slippery fleshy fronds. How much flow is needed depends on the size of the system, but in general most plants can handle large amounts of movement.

They’re many suitable substrates for growing marine plants in the aquarium. The composition, depth and size of the substrate used is largely based on the individual species of macro algae or sea grass desired. Many commercial products are available to hobbyists for use with marine plants, but most are marketed for the refugium. Although macro algae does not derive any nutrients directly form the substrate, with the exception of sea grass, some type of substrate is usually needed for most species so that they can readily attach themselves. By far, the most popular substrate is the use of a fine grade aragonite sand at varying depths of up to 6” or more. Fine grade sand is readily colonized by most all Caulerpa species and is generally the easiest to maintain. There are also proven benefits to providing a deep sand bed to reduce nitrates and to culture marine fauna, but macro algae only require about 1” or less to attach and grow. Sea grass, however, does require a deep sand bed as its root system can extend quite deep, as much as 12”.

Careful attention should be taken to not introduce substrate to the aquarium that is too compacted, such as silica or quartz sand as this will most likely cause a dense anaerobic layer in the sand bed that can be toxic to tank inhabitants if disturbed. If a mixed macro algae and sea grass system is desired, it would need to devote some portion of the aquarium to a deep sand bed in order to successfully grow vascular plants. For the most part, a mixture of substrates will create an environment suitable for the addition of most any species desired. Most commonly available substrates are composed of variable amounts of aragonite and/or calcite. Aragonite is beneficial in its ability to properly buffer the aquarium water, helping to maintain both ph and alkalinity. Smaller grain sizes dissolve faster while coarse media such as crushed coral is much slower to break down requiring a higher ph to dissolve. Marine plants that do well in a fine to medium grade aragonite sand include most species of Caulerpa and calcified algae such as shaving brush & mermaids fan, as well as sea grass.

Coarse media such as crushed coral, shell or live rock rubble can also be used to anchor marine plants and is a good choice if a deep sand bed is not needed, especially in the refugium. The only drawback to using coarse sand/rubble is that it tends to collect detritus and sediment, often becoming a nutrient trap over time. In marine plant dominated aquariums this can be an added benefit however, as high levels of nutrients are needed for long term success. Some invertebrates are better suited to this environment, such as amphipods, while other soft bodied invertebrates desire a less abrasive environment. Most varieties of red and brown macro algae grow on rocks and hard bottom habitats in their natural environment, so a coarser substrate is more suited for anchoring. Marine macro algae such as Gracilaria, Botryolcadia, Sargassum and Halymenia can be glued or placed between rocks/rubble and will readily attach themselves. Most all macro algae are very adaptable, and will grow free floating or attach to most any surface, including substrate, live rock or even the sides or bottom of aquariums.

During the early 1990’s, mud filters began to gain in popularity for use in the refugium. Several manufacturers began offering a product that would duplicate tropical coastal environments, such as lagoons and mangrove habitats. These products claim to provide a variety of trace elements including, calcium, iodine, strontium, iron, and free carbon. The idea behind the “mud” was to provide a replenishing source of nutrients by slowly releasing them into the aquarium water. These types of substrates can be problematic long term as they will often become acidic and can effect the ph of the aquarium.

Keep in mind that in any macroalgae dominated system, any type of substrate will eventually get colonized with organic material and will need to be either removed or siphoned off the surface. Limiting the overall depth of substrate in both the refugium and or aquarium can make it easier to maintain the health of the sand bed. Some hobbyists even favor a bare bottom system with no substrate and only live rock for filtration where the detritus and sediment can be easily siphoned out.

Macro algae are much more diverse than vascular or terrestrial plants in their ability to uptake and process nutrients. They generally require a larger range of nutrients in an inorganic form than vascular plants do, but are able to derive a few essential nutrients from organic compounds such as some aquarium substrates. Few studies have been done on individual species of macro algae to determine which major and minor nutrients are essential to the plants survival and growth. This is due largely to the fact that natural seawater is used in most research and aquaculture production, which typically contains such high concentrations of the major and minor nutrients needed for plants to grow that specific data is never collected. However, it is commonly accepted that macro algae and sea grasses need the same essential elements as higher plants do. Unlike vascular plants, marine macro algae must be supplied nutrients through the water column and not through the substrate. This is achieved by providing all needed elements through the aquarium water.

Macro Nutrients

The macro nutrients, or primary nutrients, that marine plants need to achieve photosynthesis are: nitrogen, phosphate, potassium, sulphur, calcium, magnesium and carbon. Some marine algae that is heavily calcified, such as Halimeda optunia, need large amounts of calcium to grow. These plants in turn produce calcium based sand as a byproduct, which accounts for the majority of all Caribbean sand.

Nitrogen

Nitrogen is one of the major nutrients required by all plants and algae, both aquatic and terrestrial. It is used by the plants or algae in the production of stored proteins. Marine plants take up nitrogen in several forms, some more effectively than others. In the aquarium they include ammonia, ammonium, nitrite and nitrate. Nitrate is preferred among all marine plants and is a readily available nutrient in most aquariums. In most marine planted tanks and refugiums there is usually sufficient amounts of nitrates available in the water column due to the nitrogen cycle and fish waste to sustain small populations of plants without adding any additional nutrients. However, in heavily planted or sea grass dominated systems it will become necessary to keep nitrates elevated just enough to encourage growth. It is commonly suggested that a range of 5-10 ppm of nitrates is acceptable in marine plant dominated systems, perhaps more in more densely populated systems. Nitrate can be added as a supplement such as KNO3 (potassium nitrate) or CaNO3 (calcium nitrate) in dry form or premixed as a liquid. Another alternative is to use treated tap water without removing the nutrients. Great care must be taken with any periodic dosing as it can be harmful to both the plants as well as fish and invertebrates in the aquarium.

Phosphorus

Phosphorus is another important nutrient that marine plants need to grow. Marine plants readily absorb phosphorus in the form of phosphate (PO4). Phosphorus can be a limiting nutrient in the growth of marine plants but it is usually sufficiently present in the aquarium due to the addition of fish food, through detritus buildup and fish waste. In comparison with nitrogen, marine plants absorb far less phosphorus so care should be taken to limit the amount of phosphate in the aquarium Phosphate levels should be maintained below 0.07 ppm to rule out as a limiting nutrient. Dosing can be detrimental, causing algae blooms.

Potassium

Potassium is absorbed by marine plants as an ion from aquarium water and is generally available in sufficient amounts in most salt mixes and tap water. Potassium is a key component that is used for photosynthesis in marine plants. Dosing is generally not needed or required.

Sulphur

Sulphur is used by marine algae and plants in the production of amino acids, proteins and chlorophyll. It is generally present in sufficient amounts in both salt mixes and tap water. Sulphur can be toxic in large quantities so it should never be added as a fertilizer to the aquarium.

Calcium

Calcium is a very necessary element for all marine plants, as it is used in the formation of cell wall structure. As mentioned earlier, some macro algae such as coralline and calcareous algae readily absorb large amounts of calcium and are composed of almost pure calcium carbonate. Calcium, alkalinity and ph are all directly connected to each other, as the availability of carbonate mostly depends upon pH and alkalinity levels. So it is important to keep all three at acceptable levels so that calcium carbonate is freely available to the plants. Ideal dosing ranges are 7-10 DKH alkalinity, 8.4-8.5 ph and calcium levels between 380-450 ppm. Most commercially available products offer a simplified solution to maintaining the balance between alkalinity, ph and calcium levels. Calcium reactors can keep calcium levels high on a constant basis so are a welcome addition to any aquarium containing marine plants and invertebrates. Not only will keeping the ph and calcium levels high in a planted tank produce healthy plants, but the amount of micro algae will decrease as well.

Magnesium

Magnesium is another element that aids in the formation of cell wall structure within marine plants and especially coralline algae. It is often directly proportionate to the calcium levels found in both salt mixes and tap water. Because magnesium is an ingredient in most commercial salt mixes it is not normally necessary to dose this nutrient. However, magnesium will be depleted quickly with the formation of calcium carbonate in both plants and encrusting algae and needs to be monitored periodically. A target range of 1250-1350 ppm is sufficient for most marine aquariums containing calcareous and coralline algae.

Carbon

Carbon is used by all living organisms in varying amounts and is particularly important in the growth and structure of vascular plants. Plants obtain carbon from carbon dioxide, which is turned into oxygen through the process of photosynthesis. Most species of sea grasses can absorb large amounts of carbon from the both their roots and leaves, while macro algae are thought to need varying amounts depending on the species. It is generally accepted that the aeration/circulation provided by the filtration system creates enough free carbon to satisfy the needs of marine plants. The process of introducing carbon into the aquarium water through carbon dioxide fertilization does little to help in the growth of marine macro algae, but it would benefit a sea grass dominated system. However, the danger of a drastic fall in ph due to over saturation of carbon dioxide could be harmful and unproductive at best so it is seldom done in the marine aquarium hobby.

Minor Nutrients

The minor nutrients marine plants need to grow are: iron, manganese, copper, zinc & molybdenum, boron, iodine, bromine. These nutrients are normally needed in very small amounts so are often referred to as “trace elements” . Most commercially available salt mixes contain all of the minor nutrients needed for marine plant growth, so they are generally replenished by regular water changes.

Iron

Iron is an important micro nutrient absorbed by marine plants and is used in respiration and photosynthesis. The most readily absorbed form of iron is iron chelate. It is available in both dry and liquid forms and can be added safely to most aquariums without damage to its inhabitants. It is unknown how much available iron is used by marine plants but studies have shown that plants benefit from improved growth and color in systems that keep it at acceptable levels. There is some debate as to the quantity that should be dosed but most hobbyists add enough iron to rule it out as a limiting nutrient. 

Manganese

Manganese is absorbed as an ion by marine plants and is used in photosynthesis. It is not normally a limiting nutrient in most marine aquariums as it is present in both salt mixes and tap water.

Copper

Copper is absorbed in very low concentrations as an ion and is used in respiration by marine plants. Marine invertebrates are very sensitive to copper so it should never be added to the aquarium water as it is present in significant amounts in both salt mixes and tap water.

Zinc

Zinc is used by marine plants in the formation of chlorophyll and is present in both substrates and tap water. At high levels it is very toxic and should never be added to the aquarium water.

Molybdenum

It is unclear what role this element plays in the growth of marine plants. In terrestrial plants it is used by the plant to break down nitrates into ammonium to be used as a source of nitrogen. Trace amounts are present in salt mixes and tap water.

Boron

Vascular plants require small levels of this nutrient for cellular membrane function, root growth and flower production. Boron has been shown to be essential for some marine algae, but not for most macro algae. Most salt mixes and tap water contain significant amounts necessary for the algae and plants that utilize them.

Iodine

It is believed that some varieties of red and brown macro algae require iodine and bromine as essential nutrients for growth. It has an obscure place in the marine aquarium hobby but is available as a supplement for species that require it.

Vitamin B12

Several species of macro algae utilize Vitamin B as an essential element of growth. It is also thought to be necessary in the growth of several sea grass species including turtle grass. Not much is know on the quantities needed as most prepared salt mixes have sufficient amounts present.

The reproductive cycle of marine algae is complex and varies greatly between red, brown and green algae. All marine macro algae produce what is known as gametes. A gamete is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. Gametes can be either male or female and are released by the development of reproductive spores on the plant. These are normally visible as a bump or node on the fronds in some species. They are known as a cystocarp when formed on red algae and are very pronounced. The spores are then released and attach to a surface or substrate. Germination of the algae spores depends upon several conditions, such as temperature, but the germination is never delayed as in terrestrial plants when conditions are not favorable for reproduction.

Reproduction helps assure each species’ survival in the ocean. Note the absence of any reproductive spores on the damaged frond in this species of Halymenia floresia (pictured above). Many aquarists mistake this orange coloration often seen on this species for new growth, but it is actually dying tissue. The drying out of cell tissue can induce the algae to produce and release reproductive spores and is used as a means of producing algae seed in the mass culture of commercial seaweeds.

When marine plants release reproductive spores, or gametes, the result is that the plant dies. This is the cycle that often occurs with species of Caulerpa in the aquarium when conditions are favorable for reproduction. When Caulerpa begin the process, they often turn yellow with little white spots appearing on the fronds or blades. A white milky substance is then released into the aquarium water. This secretion is composed of the gametes and the cell tissue of the algae. Clear tissue in most species is usually not associated with reproduction, but rather a sign of nutrient deficiency.

What causes reproduction in marine algae?

Marine macro algae reproduce when their environment changes, or when their “biological clock” say it’s time. Some of the conditions known to induce a sexual event in nature are: spring tides, lunar phases, temperature and photo period. Some species of algae are even known to release pheromones or organic chemicals to attract male gametes. Several species of marine algae however, are not affected by photo period alone and can reproduce in both light or darkness. In the aquarium the conditions are artificially maintained, so care must be taken to limit any sudden change in water quality that can induce a sexual event. Species of Caulerpa are known to not release reproductive spores if kept under constant illumination. While this may be true, its growth is typically stunted and the algae cease from productively removing nutrients as the process of photosynthesis is slowed. This is known as the 24/7 lighting cycle and is typically employed by aquarists culturing Caulerpa in the refugium.

Controlling the reproductive cycle in the aquarium

Germinated gametes or spores attach themselves to a surface such as rocks or substrate and then begin their growth. Most live rock, imported or aqua cultured, are covered in both fertile and unfertile algae spores. This is why, after several weeks or months of favorable conditions in the aquarium, up sprouts a new plant, seemingly out of nowhere. It also explains why undesirable algae such as micro algae and invasive turf algae can quickly appear and take over the live rock and eventually an entire system. The proper cycling of live rock is crucial to remove many of the undesirable algae that may reside upon the surface of the rock.

Control of both micro and macro algae growth is usually accomplished by limiting excess nutrients in the aquarium by using the correct spectrum bulbs and maintaining the temperature of a system. The turbidity of the aquarium environment will also affect growth in marine macro algae. Species that grow in protected habitats will not grow at the same rate or share the same characteristics if introduced to strong currents in the aquarium. This is evident with many species of Caulerpa, especially C. mexicana. It will remain short and compact in strong current, while growing tall and wide in a sheltered environment. Overall however, marine micro and macro algae are very resilient and will adapt to almost any artificial conditions including current, lighting, temp, salinity and ph. Another limiting factor of growth in marine algae in the aquarium is the competition for nutrients and sunlight between species. When conditions are favorable for rapid growth, eventually one species will try to dominate the landscape and “choke out” other species or colonies. This can be avoided by diligently pruning the aquascape so that no colony intrudes or outgrows its biomass or given space.

Reproduction in sea grasses

The marine flowering plants (angiosperms) reproduce by both sexual or asexual (vegetative) methods. In sexual reproduction, the plants produce flowers and transfer pollen from the male flower to the ovary of the female flower. Most sea grass species produce flowers of a single sex on each individual, so there are separate male and female plants. Some species only reproduce through vegetative means. Vegetative reproduction is a type of asexual reproduction for plants in which new plants are formed without the production of seeds or spores. In asexual reproduction, the new plants are formed by the rhizome which serves as an organ of vegetative reproduction. Shown to the left is a picture of a newly formed flower on a species of Thalassia. Flowering plants are rarely seen in the aquarium and are unlikely to reproduce by seed in captivity as conditions are not favorable. Most of the occurrences in the aquarium are from sea grasses collected just before the flowering stage. 

Just like traditional freshwater planted aquariums, the creation of a marine plant dominated system can be just as beautiful if properly cared for. The use and arrangement of marine macro algae and sea grasses in the aquarium is both functional and aesthetically pleasing. Throughout the world, there are various habitats that are unique in both their location and characteristics, providing a limitless scope for recreating natural aquascapes. 

A biotope, or species specific ecosystem, is one in which both the landscape and livestock are matched to a known environment. Although most marine plants are found in fairly shallow water environments, there are several species that are only found in deep, pristine habitats which offers the hobbyist a vast array of choices. An aquascape can be as unique and varied as you wish, depending on the species and the devotion to maintenance. Planning is a major key to achieving a more natural looking ecosystem, as plants and algae can quickly overgrow any aquarium and soon appear as a field of weeds. Macro algae will ultimately compete with other species over light and nutrients, so species specific biotopes are often more desirable for long term success. Some of the same basic rules or guidelines in setting up a freshwater planted aquarium translate to the marine system. There are basically two schools of thought concerning recreating a natural biotope. The first is to include only native plants, fish and invertebrates to reproduce an aquascape that is representative of a particular region or environment. While this can be done attractively, the amount of species will be limited. The second method is to recreate or simply represent a natural environment, allowing for a much wider variety of species and design. The ultimate goal should be to create a captivating and realistic aquascape that mimics a natural ecosystem and personal taste.