XIII. Advanced Coral - Introduction to Small Polyp Stony Coral
This article discusses Small Polyp Stony Coral, Care & Recommendations
The most abundant of "reef building" coral or Scleractinian coral are the Small Polyp Stony Coral(SPS). Similar to the other Scleractinian Corals, LPS, SPS coral possess a calcium-based skeleton, by and large, this is where the similarities end. SPS coral grows in two primary forms, plating or branching. These corals often come from the nutrient desserts of the reef crest and are much much more sensitive to pollutants than most coral. Some tanks may suffer only a loss of SPS coral to see all other corals pull through some fluctuation of chemistry or abnormality with temperature or lighting. In short SPS coral have a reputation for being more fickle than most coral, however, with their unique requirements demystified long-term care becomes obtainable.
Small Polyp Stony Coral
Represented primarily by four genera', Acropora, Montipora, Stylophora, and Pocillopora come in thousands of colors and are at the heart of the coral trades "Premium Coral" market. Branching outcrops of neon coral, dotted with often starkly contrasting polyps reach and intertwine forming the dense underwater equivalent of a jungle. Montipora, on the other hand, is unique from the others mentioned in that it is available in branching, plating or encrusting morphs. Regardless of physical form, SPS coral comprises the backbone of the coral reef in a very literal sense and are exposed to the tumultuous currents of the waves above. The rigid calcium-based skeletons protect small delicate polyps that extend to catch floating phytoplankton and very small zooplankton. These coral have an extraordinary demand for calcium and proper alkalinity to maintain this rigid protection while remaining remarkably delicate.
As the water around the reef crest is constantly oxygenated and carried away by the waves so to are nutrients and ionic bi-products created by the reef itself. This means dissolved nutrient levels are very low and oxygen levels are fairly high. It is thus harder for bacteria and other pathogens to take a strong foothold in these conditions as redox levels are high enough to thwart their spread, however, in our tanks, this may not be the case and SPS coral is known to suffer from two highly researched but still fairly mysterious diseases. To prevent this, superb care should be taken of our SPS tanks and a proper coral dip should always be used to prevent the introduction of contaminants from new additions. Additionally, it is highly recommended the aforementioned diseases(Rapid Tissue Necrosis and White Band Disease) to know thy enemy.
Care
When keeping an SPS dominated fish tank, the need for calcium and alkalinity is only met through water changes with the most frequent of changes, becoming arguably too much hassle to even consider in most systems. However, unlike when keeping LPS coral, simple two-part or kalk may need to be added at such a rate this too becomes a hassle or at the very least a significant financial dependency for the system. In cases of SPS tanks, the employment of a Calcium Reactor is highly recommended. A calcium Reactor takes the ingredients of Carbonate Media, Carbon Dioxide, tank water and combines them in a reaction chamber. The Carbon Dioxide acidifies the carbonate media, breaking it down into the water column. The elements from within the carbonate media are absorbed into the water column and introduced to the tank in a similar fashion to a klakwasser reactor, via a slow feed to the sump. The most commonly used media is ground reef rubble. Due to the risk of carbon dioxide acidifying the water in the reactor too much and causing the pH to drop, careful monitoring of CO2 and use of a pH controller is strongly recommended, if I may not outright insist.
In addition to much higher demand for stable calcium alkalinity and ph levels, these coral are exposed to far lower levels of dissolved organic compounds(DOC) than any other corals. This leads to a lower ability to tolerate and cope with nutrients. Where even some LPS tanks may see an occasional nitrate spike that regulates itself, perhaps due to overfeeding, and see no ill effects, an SPS tank may start to show visible signs of stress if any Nitrate is detectable. Truly committed reef enthusiasts have spent hundreds of dollars on ultra-low lab grade Nitrate test kits and all the equipment they can afford to assure stable nutrients within their SPS system.
Recommendations
With thousands of colors combinations available the possibilities are endless when considering Acropora alone as a tank inhabitant. Some of the most highly acclaimed displays throughout the world showcase these iconic beauties of the coral reef. Many fetch obscene prices while many more are available at quite modest costs. It is important to consider the unique care required for SPS coral, the flow required to keep the polyps exposed and the coral free of mucus would be too strong for many LPS corals; the light intensity required for the vibrant colors, too intense for many soft corals adapted to deeper depths.
Pocillopora- Available in a variety of colors this branching SPS boasts the ability to readily self reproduce in the aquarium at a success rate far greater than any other SPS. A happy Pocillopora will produce "bud" like structures it drops to form new colonies, in many cases, it has been recorded releasing gametes into the water column and new colonies forming through self-fertilization of the gametes. The ability to easily grow in captivity makes this a standout choice compared to the other coral in the SPS grouping. Many coral providers are even able to fully sustain their Pocillopora demand through aquaculture and mariculture endeavors meaning they have a very low impact(if any at all) on the reef populations.
Stylophora- The "Cats Paw" coral. Dense cropping of rounded, stub-like branches grown into nearly symmetrical clusters of bright pinks, purples, and greens. The Stylophora coral is a beautiful and comparatively durable SPS coral. While its demands for flow and water quality remains as high as the other SPS coral, Stylophora is unique in that it seems to adapt the most readily to lighting conditions. While like LPS coral they may brown or otherwise dull in color, lower light levels are possible with Stylophora and the above mentioned Pocillopora for that matter than with Acropora or Montipora. Unlike Pocillopora Stylophora does not bud and reproduce as readily in captivity, however, demand is again largely met by aquaculture and mariculture efforts and sourcing frags or colonies with no impact to the reef is simple.
Monitpora- Whether branching, plating, or scrolling, Montipora offers a stunning contrast of growth patterns to the other SPS coral. Available in solid colors, or with polyps that differ and often contract the underlying growth they offer a wide variety of color and shapes, so much so that a complete reefscape is possible within the single genus. As these SPS often occupy a lower niche on the reef, below the crest, they seem to be less demanding of light than Acropora, though high flow rates and lighting are appreciated.