XII. Intermediate Level Coral - Introduction to Large Polyp Stony Coral
This article discusses Large Polyp Stony Coral, Care & Recommendations
Upon observing an LPS colony for the first time you may notice the striking colors, the soft "fleshy" appearance, or, the tentacled lined mouths of their polyps. Beneath this exterior, however, lies a calcium carbonate based skeleton. It is this skeletal system that supports the polyp as it expands throughout the daily feeding cycles. This skeletal system, like our own, requires care and nourishment to grow and maintain its strength. It is in caring for coral with a skeletal system that we add additional requirements to our reef tank.
Large Polyp Stony Coral
Aptly named due to the relative size of their polyps. Unlike soft coral and the diminutive polyps of Small Polyp Stony(SPS) coral, LPS coral usually sports a large polyp structure. Many express their polyps through a colony as in the case of Favia or Echinophyllia while some, as in the case of Fungia are considered solitary with a single polyp making up the entire coral. All stony coral are voracious feeders, their tentacles capable of capturing prey with nematocysts. While preferred prey size varies from species to species, most LPS coral will appreciate a diet of zooplankton including rotifers, brine shrimp nauplii, and copepods. Larger, fleshier LPS may be capable of capturing larger prey but caution should be used to ensure prey items are able to be captured and completely digested.
Failure to use reservation when feeding LPS corals will result in them consuming all prey items offered. This is done by a reaction and involves a significant expenditure of energy from the coral. Once in the gut of the coral, it will attempt to digest the prey item. If the prey item at this point is too large to be digested by the coral, it will regurgitate the prey item. This again involves significant energy to be used by the coral. In the process of feeding the coral, in this case, we have made it "work-out" twice instead, the coral has expended more energy attempting to eat than it had gained from eating. In time this can lead to malnutrition and the "unexplained" loss of a colony. Additionally, the unconsumed food is left to break down in the aquarium ultimately leading to increased waste.
Instead, care should be taken to observe the coral for sometime after feeding, if you notice any coral regurgitating food it means that the prey item was likely too large and smaller fare should be offered. Remove the uneaten food so that it is not able to rot in the system and foul the water. It is a good idea to not attempt to feed this coral again right away and instead give it a few hours to a day before attempting to feed again. This gives the time for the digestive fluids in its stomach to be restored so that the next food offering may be properly digested, much of the digestive fluids within a corals gut are expelled when regurgitating food. With proper care and feeding LPS, coral can obtain a balanced amount of carbon-based energy from digestion and leverage this with sucrose based energy obtained through photosynthesis and available calcium in the water column to complete the process of skeletal genesis.
Care
When comparing LPS coral to that of soft coral and colonial polyps, the care requirements of the former are a bit more precise. Due to a skeletal structure being present in LPS coral, the maintenance of key components in the water column becomes critical to success. When forming its skeleton, LPS require elements such as Calcium and Magnesium present and in biologically accessible forms. The general rule is to maintain a Calcium level of at least four hundred twenty part-per-million(420ppm) but no greater than four hundred sixty parts-per-million(460ppm) as participation may occur. Magnesium should be maintained at a level rough three times your calcium level. For example, a tank maintained with a calcium level of four-hundred twenty part-per-million(420ppm), should have an available level of magnesium equal to one-thousand-two-hundred sixty parts per million(1,260ppm).
The easiest way of maintaining appropriate calcium and magnesium concentrations is through reliable water changes with quality salt mixes. With a tank mostly populated by soft coral with only a few LPS coral, this may be all that is needed to maintain adequate calcium and magnesium levels. However in the case of tanks that are primarily LPS, or when there is just a high density of fast-growing LPS corals, the demand for calcium and magnesium may exceed levels maintainable through water changes. When caring for systems with a higher demand for these elements the use of additives in-between water changes is used to bridge the gap. Additives may be measured and added daily, or, dripped into the system at a steady rate throughout the day.
The most commonly used additive for the maintenance of these levels is Two-Part dosing systems. Many are available but all exist as two primary additives added in ration and correspondence to one another. While exact components differ from manufacturer to manufacturer, the general perception is that one half adjusts and buffering capacity of the water by adding ionic compounds that will bind to the buffering agents and the other contains a balance of buffering agents that are now readily absorbed into the water column and taken up by the coral. An older method to obtain the same result is through the addition of "Kalkwasser" or Calcium Water, known in the states as "Lime Water".
This process is easiest with auto-top-off systems, though it can be done through stand-alone reactors. When using an auto-top-off, the freshwater is simply dosed with an appropriate amount of kalk for your tanks needs for however long your top-off reservoir usually lasts. This involves less risk of accidentally adding too much kalkwasser. When using a reactor injection method, the kalk is kept in a reaction chamber, water from the tank is mixed with the kalk and an amount of kalkwasser is created relative to the volume and flow-rate of the reactor. The kalkwasser is then ejected from the reaction chamber and introduced to the system, usually via the sump. Due to the large volume of additional kalk stored in the reactor, there is a much greater risk of over saturation. If too much lime water is created and introduced to the system it can have drastic effects on the living things in our aquarium. Whenever Kalkwasser is used a much closer eye should be kept on the reactor itself as well as your calcium, alkalinity and pH levels. Any abnormalities should be corrected immediately by either shutting down the reactor to allow levels to drop, or, add additional kalk as the reserve is consumed.
It should also be noted that specific lighting and flow requirements will differ from species to species and proper flow and lighting is critical to the health of all coral. Lighting too strong will cause damage to the soft tissue of LPS coral and kill the underlying zooxanthellae, lighting too low and the polyps will grossly over-expand in an attempt to collect more light. The density of different zooxanthellae within the LPS may change to account for light as well, many taking on a dull green/brown appearance when given inadequate light. This is due to the coral now having a higher density of zooxanthellae that require lower light levels and a lower density of the accessory pigments used to shield or otherwise convert light for the underlying zooxanthellae. Many a browned out “bulk-lot” coral has become a stunning and vibrant coral given proper lighting and care, an unfortunately for many premium coral wash out and lose their pop when proper care and lighting are overlooked.
Recommendations
While the grouping of corals referred to as LPS is very broad, there are a few that I hold near and dear to my heart. These, in my opinion, exemplify LPS corals best qualities; photo-adaptive capabilities, an interactive feeding experience, bright colors, and durability that coincides with life at great depths in the ocean. These coral seem to thrive equally well under most lighting options commonly employed and all readily eat Mysis or Brine shrimp. As these are two of the most commonly used frozen foods for fish, it means that you likely do not have to add anything to your normal feeding supplies. The above factors combine for striking beauty with low fuss maintenance easily performed by most aquarists.
Fungia- One of the oldest coral recorded by science, Fungia are solitary polyps that spend the majority of their lives on the beds of ocean lagoons. Unlike most coral, Fungia is considered non-sessile, they use specialized tentacles along the circumference of their polyps to move along the ocean floor. This process is comparatively slow, even when compared to snails, but is never-the-less observable in the home aquarium. Fungia will often move from the place first introduced, exploring lighting and flow in different areas until it finds a suitable place to settle down. In some cases, we simply cannot provide "perfect" conditions for a Fungia on the floor of our tanks. When this happens, it is not uncommon to see a Fungia, over the course of days or weeks, shimmy up the reefscape to find a better home. Should your Fungia leave the sand bed its powerful tentacles may become a threat to nearby coral. Care should be taken to clear coral from around it and make a "fall-zone" free of other coral.
Echinophyllia- Referred to in the trade as a "Chalice" coral, Echinophyllia comprises a genus of three readily available species. Additionally, due to the confusion of taxonomy, the "chalice" and by extension Echinophyllia nomenclature are often assigned incorrectly to similar coral such as Mycedium and Echinophora and Oxypora. For all intents and purposes, these corals are easily confused especially when we consider demographical overlaps, morphological oddities, or a human error in transposing information from one place to another. All have similar growth patterns and form a large encrustment on the substrate before growing upwards into spectacular cup-like formations. Available in a wide variety of striking color patterns, Chalice coral is a staple in the industry and remain one of the top "designer" corals making waves whenever a new variant is discovered.
Duncanopsammia- Duncanopsammia axifuga, more commonly referred to as "Duncans Whisker" or more simply "Duncans" is an extraordinary example of colonial Large Polyp Stony Coral. Unlike most branching LPS, the branches of the coral have tissue covering the underlying carbonate based skeleton. Not only that but this tissue is a bright often neon mix of yellow and green. A top each branch are a cluster of equally beautiful, neon green flower-like polyps. Flowing in the current they resemble a field of psychedelic sunflowers the tentacles, petals in the wind. Beyond a striking appearance, Duncans also display extraordinary growth rates when fed regularly in addition to proper lighting. However, in lower lighting conditions, Duncan's owners may be happy to see an equally dense cluster of polyps by simply feeding the polyps more to compensate for lower light availability, within limitations of course.