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What are SPS corals? It is a type of hard coral, and we can expand this acronym to Soft Polyp Stony, or Soft Polyp Scleractinian.

Compared to LPS (soft corals), SPS corals are characterized by a large number of small polyps. They are less aggressive and have a hard skeleton, made of calcium carbonate, covered with thin tissue. SPSs occur in branched, plate forms, enveloping the rock.

In this article, we will discuss the key considerations for keeping hard corals in a saltwater aquarium at home. Let’s start!

Water circulation

SPS corals require a lot of water circulation. Stronger circulation allows them to obtain more nutrients, and it also allows them to cleanse themselves more efficiently.


SPS corals live in symbiosis with algae called zooxanthellae. Zooxanthellae need light to carry out the photosynthesis process. The culmination of this process is the production of energy, which the symbiotic algae give back to the corals. For this to happen properly, we need to provide the organisms with high-quality light, which will allow the coral to leave less zooxanthellae, resulting in a brighter and more pronounced color. In poor lighting, the coral will increase zooxanthellae, which will cause the coral to have a brownish tint.

Clean water

SPS corals like clean water. This means that the final content of NO3 and PO4 should be low. When keeping Acropora SPS corals, the recommended NO3 value is around 0.5-1 mg/l and PO4 is 0.08 mg/l. It is also recommended to use the right amount of activated charcoal on a regular basis. It is usually replaced every 4 weeks.

Constant water parameters

SPS corals require stable water parameters. They are the most sensitive of all coral types. This means that they like not only that the relevant parameters are in the norm, but also that they are kept at a constant level. Of course, you can change a given parameter, but you have to do it slowly. Corals from this group, in addition to being sensitive to temperature and salinity changes, are also sensitive to the KH and PO4 parameters. A change in the level of calcium or magnesium doesn’t affect them so much. Acropora corals can have problems and start bleaching when the KH level changes by up to 1 dKh during the day. Regular tests should be carried out and the correct preparations should be dosed.

In order to maintain constant water parameters, we must divide this part into two: testing and dosing fluids.

Testing water parameters

Basic water parameters:

  • KH – 7-8 dKh
  • Ca – 400-440 mg/l
  • Mg – 1250-1450 mg/l
  • PO4 – 0.06-0.08 mg/l
  • NO3  – 0.5-2 mg/l

These elements can be tested with ordinary drop tests. KH, PO4 must be tested at least once a day. If the aquarium is stable, then Ca, Mg, NO3 can be tested 2/3 times a week. If we are not sure about the aquarium, we test KH and PO4 several times a day, and Ca, Mg and NO3 once a day.

Let’s remember that the parameters mentioned above are just the basis, which is not enough for SPS corals. We also need to ensure the appropriate level of other ingredients. To check the level of more elements, we can do an ICP-OES test. If we have a stable aquarium and we have established supplementation, then the ICP-OES test can be performed once a month. If we determine supplementation or there are problems, we should send water for analysis every one or two weeks.


If we already have set parameters and drops on given parameters, then we set the appropriate dosing for it. The easiest way is to dose 3 components with minerals. There will be a lot of macro and micro elements in these components. One, two or three-bottle components can be found on the market. I recommend three-part preparations, because in this version we get a much wider range of minerals.

I participated in the development of these types of products and in the process we tested different versions from different manufacturers. Each of them is based on a different vision related to the composition of the product. But I will leave that topic for a future article.

In my opinion, the simplest dosing method is three components (tests are carried out daily manually or with an automatic KH measuring device), we keep KH, Ca, Mg at the appropriate level. From time to time, we send an ICP test and correct the doses of minerals with the use of dedicated products for specific elements.

It is also worth mentioning here that there are methods on the market that allow you to automate a lot. There are devices for testing and dosing specific elements. All you have to do is set the appropriate frequency of measurements in the application, and the dosing of liquids on the pumps, and you don’t have to think about the often troublesome testing and dosing of liquids based on KH anymore.

No water pollution

As I’ve already mentioned, it’s crucial to maintain constant water parameters. However, constant water parameters mean no contamination or overdose. By performing regular tests, including ICP, we can control these issues.

Water pollution is currently a mega bane in marine aquaristics. In our company, we perform the ICP water testing service. In the future, I will create statistics for you to determine how many aquariums, in relation to the number of all sent tests, have or had problems with water contamination.

Many people do not realize that there is a silent killer lurking in their aquariums and that some equipment or metal element is dirtying their water. The effect of dirty water on SPS can be catastrophic. After exceeding certain values, some parameters will be deadly for corals. There can be many of these parameters. For example, if your impeller will rust and it is made of brass (often found in the construction of impellers), then in the water test you will come up with exceeded copper, aluminum, zinc, tin, iron, manganese, and even lead or chromium. Each of these elements in excess will poison animals. Of course, some are more toxic than others. On the other hand, some corals react more to this element and others to another.

I’ll write a dedicated article for you and delve into the details of this topic. Look out for it on ReefPedia.

I think it is worth emphasizing once again that if you want to have beautiful SPS corals, you must ensure that there are no pollutants in your aquarium.

High, constant pH

All marine animals like a sufficiently high and constant pH of the water. However, in the case of SPS corals, this is a key issue. Many mineral absorption processes, or other metabolic processes, take place more efficiently at the right pH level. We can say that a pH between 8.2-8.4 will be ideal for keeping SPS hard corals.

If you’re having trouble getting your tank’s pH level right, check out these articles:

The most popular SPS corals

  • Acropora (tenuis, microlados, echinata, loripes, granulosa, and many, many more), 
  • Montipora
  • Seriatopra
  • Stylopora


If you want to have beautiful SPS corals, you need to take care of several important areas. When entering this world, you can start with simpler SPS, such as Monitopora, Seriatopora or Stylopora, and leave the more sensitive Acropora for the end. It’s worth keeping SPS corals, if only because once we learn to work with them, they will repay us with beautiful colors and fast growth (here, of course, fast growth is different in different varieties).

Let’s talk about SPS on Social Reef! Feel free to discuss in a dedicated thread 🙂

About the author

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Marek Protasewicz

Reefkeeping has been my passion for over 10 years now. I love learning. The hobby has taught me many valuable lessons, patience being the best example. Combining work and passion is my path. I run Crazy Coral, a marine aquarium shop, for a number of years. Building this business from the scratch I learnt from my own mistakes at a heavy cost.
Later I managed a project aimed at development of methods for quick growth of Corals in non-natural conditions. The project was carried out by Get Sales, Poland. Presently, I am responsible for distribution strategy at Reef Factory, of which I am a co-founder. The company produces smart devices for marine aquaristics. The last projects I have been involved in are Social Reef and ReefPedia.

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