CORAL & CLAM HUSBANDRY

 

Coral and Clam Husbandry Principles

Coral and clam acclimation is a specialized task and the rule of thumb is to be careful and safe. One of the key special considerations is proper light acclimation without which corals can bleach, burn, or become severely damaged.

While most hobbyists are very diligent about conventional water temperature and water chemistry acclimation, coral light acclimation remains somewhat unfamiliar. After carefully researching the light requirements of a particular coral, many reef hobbyists are anxious to immediately place new corals in the brightest location, closest to the light source. This may seem appropriate, but in many situations, it can cause more harm than good.

 Keep in mind that lighting conditions vary from aquarium to aquarium. No two fluorescent , LED, or metal halide systems have identical light properties. Therefore, a coral acclimated to artificial lighting from one system (e.g., a pet store or an online retailer) will need to gradually adjust to different lighting conditions when introduced to a new aquarium system. 

Regardless of your light setup, place all new corals on the bottom of your aquarium until they begin to adjust. If you employ metal halide lights, place some sort of screening material above your coral during the first few weeks of acclimation to attenuate the light. The screen could be egg crate, light paneling or fiberglass mesh. Also, reduce the photoperiod by a quarter for the first week and gradually add an hour each week to reduce the risk of initial light shock. A good indication your coral has adjusted is when it appears fully expanded and displays full coloration.

Slowly inch the coral to its preferred location over the next month or so. Generally, brighter colored corals should be nearer to the lights. Bright colors signify tissue pigment development that helps protect coral from the UV-light present in shallower depths. Though proper light acclimation is a slow process, it can be the difference between a home reef that simply sustains and one that thrives for years to come.

Coral Handling

 Different corals require different handling techniques. For instance, soft corals, polyps, and mushroom corals will normally arrive attached to a small rock. Only handle these corals by the rock, this way you can avoid touching the polyps. Hard corals with large fleshy polyps can be handled by their base, which is the hard exoskeleton. Other hard corals, including SPS corals, should be handled only by the base where it was fragmented, or by the plug or rock it is attached to. A pair of gloves is highly recommended in handling all corals and will reduce the possibility of irritating the coral when handling it. Furthermore, always handle all corals gently in order to minimize the chances of damaging the specimen.

Coral Compatibility

Very careful attention must be paid to the placement of corals in the reef tank visa vis coral compatibility. Many corals are extremely aggressive hunter/feeders and can inflict severe damage on non-compatible tank mates if not properly separated from them. 

Depending on the species and particular circumstances, corals may employ one or more of the following aggressive mechanisms:

 

  • Rapidly overgrowing neighboring invertebrates—i.e., actually growing directly onto the neighboring colony or extending over it and preventing it from receiving life-sustaining light
  • Stinging neighbors with nematocyst-laden tentacles
  • Extruding digestive organs (called mesenterial filaments) and essentially digesting the tissues of adjacent corals
  • Exuding toxic chemicals (e.g., terpenoids) into the water to kill neighboring corals or impede their growth

What can you do to counteract these hostile tactics?

  • Research your corals thoroughly before you buy them - A little modest research on the characteristics of different corals will reveal all kinds of vital information regarding their relative aggressiveness/noxiousness. For example, Sarcophyton leather corals are notoriously toxic and various Euphyllia corals are known to produce long, stinging “sweeper” tentacles. Such details must be taken into account when choosing which species to combine and how to situate them in your tank.
  • Space your corals out properly - When placing specimens, allow more room between them than you think they’ll eventually If the tank looks sparse initially, that’s okay. It’s better to have a smaller number of specimens with plenty of room to stay clear of each other’s tentacles than to have a larger number growing on top of one another and in a state of constant warfare.
  • Isolate rapid-spreading corals - Corals/polyps that form encrusting mats and grow rapidly outward onto adjacent substrates, such as green star polyps and certain zoanthids, may need to be isolated to a single, separate rock—an island, if you will—to keep their growth in check and prevent them from irritating or overgrowing cnidarian
  • Maximize water movement - Brisk, turbulent water movement, which is beneficial in many reef- aquarium settings anyway, will help prevent toxic chemical compounds from concentrating around any particular specimen. Keep in mind, however, that not all sessile invertebrates appreciate a high level of Some, such as Discosoma spp. mushroom polyps prefer very low levels of water movement.
  • Employ a protein skimmer, chemical filtrants, and copious water changes - Vigorous protein skimming and chemical filtration with activated carbon will help remove/adsorb the byproducts of coral chemical warfare. And, of course, you can add the removal/dilution of these toxins to the many virtues of regular partial water

The rule of thumb here is that if your coral has tentacles, chances are it is one of these aggressive species (including, but not limited to Catalaphyllia sp., Galaxea sp., Euphyllia sp., Goniopora sp., Heliofungia sp. Fungia, sp, etc.), however, many “fleshy” LPS corals like Trachyphyllia sp. and Lobophyllia sp. can also extend feeding tentacles and sting their neighbors. Anemones are also obviously aggressive “stingers” and should be placed sufficiently far from corals so that their tentacles cannot inflict damage.

Although mushrooms and polyps are relatively harmless, there are some species that can be semi-aggressive to their neighbors. Same thing applies to “softies”, some of which can secrete toxic chemical compounds from their tissues.


Take a good amount of time to research the species you want in your aquarium to see how aggressive they are! Separate all aggressive species sufficiently from their neighbors. It won’t be difficult to see if they are far enough away because if they are not you will soon notice necrotic (dead) spots on the “victims” in the areas closest to the “stingers”. Also, make sure to re-evaluate the separation as your corals grow and encroach upon each other.

A little precaution and some constant attention will yield invaluable results and allow you to maintain and enjoy a successful reef aquarium for years to come.

Coral Coloration and Your Aquarium Lighting

There are many environmental reasons why corals may change color. However, in home reef aquariums, the most common cause of dramatic color change is due to lighting. 

Corals react to light by adjusting the number of cells responsible for utilizing light, as well as the pigments that provide protection from strong light. What we perceive as color change is, in fact, the coral's natural response to a particular light source. Corals will strive to achieve a balance where the number of cells and amount of pigment matches the corals' needs for both nutrition and protection.

 

Light intensity and coral color

Many corals have the ability to adapt to different light intensities. For example, photosynthetic corals with special, light sensitive cells called zooxanthellae cells. These symbiotic cells contain chlorophyll and provide nutrients to the coral in exchange for protection. To ensure a continuous source of necessary nutrients, the host coral regulates the number of zooxanthellae cells and amount of chlorophyll within those cells. One of the basic criteria for zooxanthellae cell and chlorophyll regulation is light intensity.

 

If the light is more intense than what the coral is accustomed to, then one of two things may occur. Either some zooxanthellae cells will be expelled from the coral or the amount of chlorophyll within those cells will be reduced. Having excess zooxanthellae cells in a brightly lit environment can be dangerous to corals.

Under intense light, oxygen generated as a by-product of zooxanthellae photosynthesis can accumulate to toxic concentrations within the coral.

 

In contrast, if light intensity is lower than what the coral usually receives, the photosynthetic zooxanthellae cells will not be able to produce the sufficient amount of nutrients for the host coral. Subsequently, the number of zooxanthellae cells, as well as the amount of chlorophyll within those cells, will increase in an effort to capture more light energy.

 

So how does zooxanthellae cells and chlorophyll concentration affect coral coloration? Zooxanthellae cells range in color from a golden-yellow to brown and large numbers of these cells give the coral a brown appearance. In other words, light intensity alters the color of photosynthetic corals by affecting the concentration of both zooxanthellae cells and the amount of chlorophyll present within those cells.

 

Therefore, in less intense lighting conditions, photosynthetic corals will appear darker brown since the corals host more zooxanthellae cells to produce more nutrients. If the same coral is placed under intense lighting, zooxanthellae cells will be expelled and the reduced amount of chlorophyll will give the coral a lighter appearance.

Color change due to light spectrum

The light spectrum, or color temperature, of aquarium lighting will also alter the appearance of corals. In general, bulbs with lower Kelvin ratings will cast a "warmer" yellow light while bulbs with higher Kelvin ratings will produce a bright, crisp, white to blue light. Different light fixtures with different spectrum bulbs impart varying color effects on corals. For example, bulbs that emit light heavy in the actinic blue range bring out dazzling fluorescent colors not visible under full spectrum daylight bulbs. While different hobbyists prefer different combinations of light spectrums, a typical lighting system for a reef aquarium consists of 50% white light with a high Kelvin rating and 50% blue, actinic light.

Color change due to UV light

 

In nature, ultraviolet light waves (UV-A and UV-B) penetrate the ocean's surface but are filtered out as the light travels through the water. Both UV-A and UV-B light waves have been found to cause destruction of DNA and RNA within coral tissue. In response, many corals have made adaptations to reduce the effects of these harmful rays. These corals developed protective pigments that are often blue, purple, or pink in color. Most corals that contain these pigments come from shallow waters where the amount of UV-A and UV-B light is higher than in deeper areas of the reef.

In home reef aquariums that rely on metal halide lighting, it is important to protect corals from UV light. Coral without these protective pigments as well as shallow water corals that may have lost their pigments during transportation are especially susceptible to the effects of UV light. Fortunately, preventing any UV light from entering the aquarium is as simple as employing glass aquarium canopies and making sure the protective glass lens on the metal halide fixture is properly installed.

It is not uncommon for corals with these bright colors to adjust to the lower UV-A and UV-B conditions found within home aquariums. The loss of colorful pigmentation is not necessarily a sign of an unhealthy coral - it is simply a normal coral adjusting to its new environment.

It is a common misconception among many hobbyists that color changes in newly received coral is an indication of unhealthy coral. Many times the color change is merely the result of corals adjusting to the new lighting intensity, spectrum, and change in UV light. With this in mind, it is important to consider the color of newly received corals and understand their lighting requirements. Be sure to properly acclimate corals to new lighting conditions and allow time for them to establish their coloration.

 

Using Reef Supplements Properly

Your success at keeping aquarium corals and invertebrates depends upon your success at recreating natural conditions. In the ocean, there is a constant source of vital minerals, nutrients, and vitamins. In a closed aquarium environment, some of these essential minerals are depleted as corals and invertebrates use them to grow.

Aquarium additives replenish essential mineral and nutrient levels to provide an ongoing source corals and invertebrates need for proper growth, physical strength, biological function, and coloration. They also help the organism resist minor changes in water conditions, as well as diseases.

 

While the addition and maintenance of calcium and alkalinity in reef aquariums is well recognized, the replenishment rate of other specific minerals and trace elements is not as well understood. Use the following chart as a general guide when selecting the appropriate supplements for your corals and invertebrates. Always follow the manufacturer's recommended dosage directions.

 

Small or Large Polyp Stony Corals, Giant Clams

 

Calcium

Helps build skeleton/shell

Strontium

Helps build skeleton/shell

Magnesium

Helps prevent premature calcium precipitation & helps stabilize pH and alkalinity

Buffer (Alkalinity)

Helps build skeleton; Buffers pH & helps maintain proper calcium levels

Iodine/Iodide

Helps heal damage due to excessive light exposure

Trace Elements

Helps facilitate enzymatic and photosynthetic reactions

Plankton Suspension

Provides nutrients that are not produced by the target organism

Vitamins

Helps maintain health, color; and facilitates biological reactions


Leather Corals, Polyp Corals, and Mushroom Anemones

 

Calcium

Helps maintain high pH

Strontium

Helps with proper health & growth

Magnesium

Helps prevent premature calcium precipitation

Buffer (Alkalinity)

Buffers pH

Iodine

Helps enhance coloration & coral expansion

Trace Elements

Helps facilitate enzymatic & photosynthetic reactions

Plankton Suspension

Provides nutrients that are not produced by the target organism

Vitamins

Helps maintain health, color; facilitates biological reactions

Crustaceans and other Motile Invertebrates

Magnesium

Helps prevent premature calcium precipitation & helps stabilize pH & alkalinity

Iodine

A component of the animal's exoskeleton; aids in molting process

Trace Elements

Helps facilitate enzymatic reactions

Vitamins

Helps maintain health, color; facilitates biological reactions

Buffer (Alkalinity)

Buffers pH