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Small Polyp Stony Corals

Small polyp stony or SPS corals are some of the most easily recognized and iconic coral species and in most cases, some of the most difficult to care for properly in an aquarium. The skeletons of these colonial animals have built the Great Barrier Reef and other reefs around the world for millennia. As these corals grow on the reef, they assimilate food and nutrients from the water swirling around them to feed and build the calcareous skeletons that become the foundation of the reef. Not too long ago, caring for these animals in an aquarium was considered impossible, with only the most advanced professional aquarists capable of keeping them alive. Over the last twenty or so years, there has been a huge leap forward in knowledge, equipment and the number of people able to get SPS corals to thrive in captivity.

There are thousands of species of SPS corals; each with their own specific needs for lighting, water flow, nutrition and other essential husbandry considerations. This page will discuss these considerations in very broad detail, as the requirements for each species would easily fill several volumes and we are learning more every day. To inform our clients about how we care for the corals in the reef tanks in their homes and businesses, here is a brief overview of these extraordinarily delicate and beautiful animals:

Common SPS Species

Some of the most common SPS genera found in local and online retailers include:

  • Acropora spp.
  • Montipora spp.
  • Pocillopora spp.
  • Seriatopora spp.
  • Stylophora spp.
  • Echinophyllia spp.
  • Hydnophora spp.
  • Pavona spp.
  • Psammacora spp.
  • Many, many others

Lighting Requirements

Generally, SPS corals tend to prefer brighter, more intense lighting higher in the water column but it is very important not to place a new coral frag in the brightest light right away. In most cases, this will shock the photosynthetic zooxanthellae algae living in the tissue and kill it, thereby killing the host coral. A much better approach is to acclimate the coral slowly, moving it higher in the water column over time and allowing it and the symbiotic algae to adjust before moving it again. Since each SPS coral species has slightly different lighting requirements, you’ll want to select (or have us select for you) lighting that allows you or us to tweak the intensity and light color mix in small increments or adjust the height of the lighting.

Coral lighting tends to be more expensive than other types of aquarium lighting but if you really want a thriving, growing reef tank, this type of lighting is absolutely essential. Which type of lighting, i.e. LED, sodium halide, fluorescent or a mix of all three will be best for you is largely dependent on your budget, the types of corals you want to keep and the skill and experience of the aquarist caring for your system. As with many aspects of coral husbandry, there are many ways to achieve success but trial and error can be costly and demoralizing.

Water Flow Requirements

SPS corals prefer the shifting currents in their native habitats, with strong, laminar flows interrupted or enhanced by other currents. Observe the small polyps on a healthy SPS coral in your local fish store, public aquarium, online retailer or in a friend’s home or business: note the posture of the polyps and individual tentacles on each polyp as they are alternately buffeted by stronger currents and sway back and forth by lighter flows. On the reef, these swirling current deliver food to the polyps to feed the colony and remove waste as each polyps digests and assimilates the nutrition. There are many powerheads or water circulation components and/or controllers that allow you to tweak the current based on the corals in your tank, with many of them having preprogrammed modes to select from. Getting the flows for your corals dialed in is one of the more technically tricky aspects of reefkeeping but essential for the overall health of your corals.


Whether or not supplemental feeding is necessary for your corals is largely dependent on the species, the quality of the lighting, the life support components built into the system, and other considerations that will likely be specific to your reef tank. Many SPS corals will require little to no feeding as long as the zooxanthellae are happy and healthy. However, if you want explosive growth and exceptional polyp extension, you should plan on regular feeding of Artemia nauplii (brine shrimp larvae,) rotifers, and other small, cultured live foods. You can also buy marine plankton in bottles but you must take great care not to overfeed your corals and trash your water quality.

Water Quality

The water quality requirements of a reef tank is another topic that could fill volumes and it is enormously helpful to have a good understanding of chemistry to fathom how concentrations of one water quality parameter positively or negatively affect other parameters. For the purposes of this article, we will provide the most critically important parameters to monitor and the best-recommended concentrations.

  • Ammonia – 0
  • Nitrite – 0
  • Nitrate – As close to 0 as possible.
  • Calcium – 375-450 parts per million (ppm)
  • Magnesium – 1300-1350ppm
  • Carbonate hardness – > 125ppm (Many reefkeepers use alkalinity and carbonate hardness interchangeably but they are different values)
  • Salinity – 35ppt (parts per thousand) or 1.026 specific gravity
  • Phosphates – As close to 0 as possible
  • pH – 8.1-8.3
  • Temperature – 78-82F

It is critically important to conduct regular water quality tests to determine the levels of these parameters and record the results. The tests are an invaluable insight into the suitability of the water for corals and the overall health of the system. Through regular testing and recording, you can then track trends over time and see how regular water changes and other routine husbandry affects these values and in turn, become a more informed and capable coral aquarist!

Professional Coral Reef Service and Maintenance in the Portland Area

If you love the look of a stunning coral display in your home or business but would prefer to leave the maintenance to the pros, give us a call today at 503.784.4403. Our skilled aquarists maintain many coral systems in bars, restaurants, businesses and private residences in and around PDX and have years of experience maintaining healthy corals and life support systems. If you are looking for a new Portland aquarium service for an existing system or would like to have us design and build one for you, just give us a call or fill out a contact form for a prompt reply and let’s get started!

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If you are interested in discussing a professional aquarium maintenance program for your system(s) with Mr. Fry, contact Aquarium Services of Oregon LLC to schedule a consultation.

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