Demystifying SPS Coral Care
by Reefer Matt

Hello Reefers! I thought I’d share my thoughts and experience with SPS coral and how I care for them. In this article, I hope you’ll find something to take with you, and apply it to your tank.


Reefer Matt’s 75 Gallon SPS Tank

First, I’d like to start by addressing the notion that all SPS coral are difficult to keep. It’s not true. While they are generally suggested for experienced Reefers with a tank aged around a year, there are a few exceptions. Those brand new to reefing may have difficulty with any coral at first, but after they’ve gained knowledge and experience, it all becomes easier. The same is true with SPS coral.

SPS coral require stability. What that means is not constantly fooling around with light settings, or pressing all the buttons on wave makers, etc. Picking a setting and leaving the coral alone will go a long way in their health. The tricky part is that you have to guess which settings are adequate if you don’t have the tools to measure them. I always recommend using a par meter to help get lighting dialed in, but it’s not a requirement. More on that later.

Water Chemistry
Water chemistry is an important factor in keeping SPS coral. The Reefer should have an understanding of alkalinity and how to control it. SPS coral have a calcium carbonate skeleton that require sufficient levels of Alkalinity, Calcium, and Magnesium to grow. There is a broad range of suggested values for these, but I’d like to recommend what I think will give you the best success. Specific gravity should be between 1.024-1.026. Alkalinity will work well at 8-9 dkh. Calcium has a bigger window at 375-475 ppm. And though a little harder to test, I like to make sure the magnesium is around 1300-1400. Choosing a salt mix that has these values will help keep them stable, but alkalinity can be adjusted before use if necessary. For temperature, I aim for 77-80F. Success can be had outside these ranges, but I find this is the sweet spot for my tanks.

Nitrate and Phosphate
Nutrients like nitrates and phosphates can vary wildly. The commonly suggested “low” values, aren’t always true. If you are having success with LPS coral at a certain level, then trying SPS there is a good place to start. My SPS tanks have a nitrate range of 15-35 ppm, and phosphate around .03-.05 ppm. I prefer to keep nitrate around 10-15 ppm, but honestly haven’t noticed any ill effects. That may be because I keep a very strong CUC in my tanks, and algae is always at a minimum.

Ph will swing according to the environment that the tank is in. For example, a closed up room occupied with people and/or pets will lower Ph, because they emit CO2. This creates carbonic acid in the tank, and lowers Ph. I try to keep Ph around 8 - 8.4 as much as possible. Opening windows (in favorable weather), using a CO2 scrubber, and dosing alkalinity boosting elements (when required) can all help increase Ph. All in all, I don’t focus too much on chasing Ph, but I do pay attention to it.


Top View of Reefer Matt’s SPS Tank

Lighting is important for all photosynthetic coral. Specifically, it’s important for the symbiotic zooxanthellae that live in the coral’s tissue. Those dinoflagellates (yes, that’s right!) provide the coral with energy to live. In turn the coral gives them a safe place to reside. More par isn’t always better. There are limits, and the coral will tell you by bleaching, or worse, polyp bailout. Finding the sweet spot to feed the zooxanthellae without “baking” or “shading” them is key to success.

In general, a range of 150-300 par with an adequate spectrum will grow healthy SPS coral. Higher par values are achievable and sometimes desired, but usually for peak coloration of the coral. I suggest staying in the lower range if trying SPS for the first time.

When lighting is too low, the coral usually turns a darker hue, often brown. This is the zooxanthellae trying to absorb more light. The opposite happens when lighting is too high. The coral will appear pale and faded. Acropora can shift colors and shades dramatically, and they probably will at first. This makes us think we did something wrong, but it’s just because our parameters don’t match where the coral came from. In time, they usually bounce back after being acclimated for many months (or longer!). But I wouldn’t declare defeat because of shifting colors as long as the polyps are extended. The key is to keep lighting stable, and only intervene if the coral start to become pale, as too high of light will kill faster than too low.


SPS coral require a lot of flow. I believe this is because they need more oxygen exchange than most coral due to a higher rate of photosynthesis from the zooxanthellae. Trying to quantify that flow is difficult, to say the least. There aren’t any portable hobby grade flow meters to measure flow, so at best it’s a guess. Luckily the coral can adapt within reason. At a minimum, you should always see water moving around in every corner of the tank. The polyps on the coral should be dancing around, but not constantly blown sideways like in a hurricane. Random, indirect flow is what to shoot for here.


Closeup of BigR Walt Disney Tenuis

If you are having issues with color on your SPS coral, flow can be adjusted instead of lighting in some cases. Lighting and flow go together like “peas and carrots”. If the coral are pale, try increasing the flow. If they are browning out, try decreasing it. I recommend adjusting one thing at a time for a couple weeks to see what corrects the issue. By tweaking lighting and flow, you can get those polyps out and color up the coral. But do it gradually over the course of weeks to months, not days.

Slow tissue necrosis and rapid tissue necrosis are terms to describe when a SPS coral has had enough, and is sloughing off its tissue. The direct cause of this is unknown, but widely suggested to be from instability in parameters like alkalinity. Anyone who keeps SPS coral will likely run into this at some point. Some claim it is contagious to other coral. I have not experienced that myself.

What I do when I see tissue loss is keep an eye on it. If it keeps progressing, I will cut the coral just above the dead spot and remount it. It’s about a 50/50 chance, but better than doing nothing. Redipping the coral may also help, but really there is no “cure”. My best guess is that STN/RTN is a range of things that create the same symptom, but the cause is unique in each case. This may explain why some see it as contagious, while others do not.


STN on an Acropora frag

Misc. Advice and Ramblings

There are a few items that I haven’t addressed like substrate, rockscape, and dosing. For substrate and rock, I suggest going with what you like. As long as you follow basic reefing husbandry, those won’t affect your success much with SPS coral. Dosing (in a newer tank) won’t be required for a year or two in most cases. I suggest doing water changes as required to maintain alkalinity and calcium at first. When the tank starts to deplete those faster than a routine water change can handle, then consider dosing. That also goes for trace elements and the “magic potions” like aminos, etc. In an established tank that is already being dosed, you may have to make adjustments as the coral grow.

It is hard to keep different types of coral happy at the same time in a mixed reef tank. I was advised early on to setup a SPS only tank for SPS coral because it’s much easier. In a mixed reef, you have many different species that all like different parameters. Some want low light and low flow, for example. Some want high nutrients. Frankly, I’m always amazed to see the tanks of those who pull it off.


Side view of Reefer Matt’s SPS tank

Some beginner SPS coral to try include: Montipora, Pavona, Leptoseris, Pocillopora, Seriatopora, and Stylophora. You can see that I have most of those in my SPS reef tank. I suggest waiting until your tank is at least 8-12 months established before introducing SPS coral for best success.

In summary, my best advice to keeping SPS coral is to provide stability, have patience, pay attention, and do the required maintenance. Adjustments will probably be needed at first. Just keep them small and gradual until you find the sweet spot for your tank. Then don’t touch it! Lol! In time you will find out that SPS coral aren’t all as difficult as you’ve heard. Happy Reefing!

-Reefer Matt