The Pale Edge

The Pale Edge

There is a specific kind of regret that comes with watching a Scolymia coral go pale. It starts at the edges of the fleshy disk, a subtle translucence that wasn’t there the day before. Within a week, the rich red or green or orange has faded into something closer to beige. The coral is alive. It is not thriving. And for most keepers, the mistake happened in the first hour the coral was in the tank.

Scolymia, sometimes called “donut” or “meat” corals by the trade, are among the more demanding LPS species to transition into captivity. They are collected from deeper, darker reef slopes than most stony corals, and the lighting intensity of a standard reef tank can be a shock that no drip acclimation routine can undo. A hobbyist in the western suburbs of Melbourne learned this the hard way with a specimen that arrived on a Tuesday afternoon in late November.

The Heat Pack Had Already Gone Cold

The coral arrived via overnight freight, packed in a styrofoam box with a heat pack that had already cooled below useful temperature. The shipping water temperature was 18.7 degrees Celsius — low, but not critically so for a short transit. The Scolymia, a green specimen with red striations, looked deflated but intact. The polyps were not extending, which is normal for a stressed coral. The mistake was already being set up: the tank it was going into ran two Radion XR15 lights at 65% intensity for eight hours a day.

“People think Scolymia are easy because they’re fleshy and they look tough,” says Renata, who runs a coral importing business out of a garage in Sydney’s northern beaches. “But they’re coming from twelve meters down. They haven’t seen bright white LED light in their lives.” She estimates that roughly half the Scolymia losses she hears about happen within the first ten days of the coral entering a customer’s tank, and that the cause is almost always lighting, not water chemistry.

The key parameter to understand before the coral arrives is par, not pH. A Scolymia that came from a shaded overhang at ten meters depth was living under perhaps 50 to 80 PAR. A typical mixed-reef tank running moderate LEDs will hit 150 to 200 PAR at the sand bed. The difference is not subtle. The coral’s symbiotic zooxanthellae, the algae that provide color and energy, cannot adjust to that shift in a matter of hours. They either expel — causing the pale, bleached look — or they die, taking the coral with them.

Seventy-Two Minutes to the Sand Bed

The standard advice for any coral is to float the bag for fifteen minutes, then drip acclimate for forty-five minutes to an hour. For Scolymia, that timeline is not long enough. The subject’s mistake was following that exact routine: float for fifteen minutes, drip at two drops per second for forty-five minutes, then transfer the coral to the display tank. The total time from bag opening to the coral touching the sand bed was 72 minutes. That is not nearly enough time for a coral that has been in a dark bag at 18 degrees to adjust to a tank at 26 degrees and a salinity of 35 parts per thousand.

The better approach, learned later and applied to subsequent specimens, is to extend the drip acclimation to at least two hours. The key is not the water volume that passes through the drip line. It is the rate of change in temperature and salinity that matters. A slow, gradual shift over two hours gives the coral’s cells time to adjust osmotic pressure without rupturing. The subject found that using a longer drip tube — a meter of airline tubing rather than the standard 30 centimeters — gave a slower, more consistent drip rate that was easier to control.

One detail that the subject overlooked entirely: the shipping water should be tested before any drip begins. The ammonia level in the bag was 2.0 ppm, which is high but not unusual for a coral that has been in transit for 24 hours. The drip acclimation diluted that ammonia gradually, but the coral was still exposed to elevated levels for the entire first hour of the process. A more careful approach would be to test the bag water, then do a small water change with tank water in a separate container before starting the drip — essentially a “pre-dilution” step that drops the ammonia before the slow acclimation begins.

PAR 145 at the Sand Bed

This is where the subject’s loss of color originated. The Scolymia was placed on the sand bed directly under the center of the Radion fixture. The PAR reading at that spot, measured with a Seneye, was 145. That is not an unreasonable number for most LPS corals. For a Scolymia that had been living in deep shade, it was a burn.

By day three, the green tissue around the mouth of the coral had started to recede, pulling back from the skeleton in a thin, white line. By day seven, the green had faded to a pale yellow-green. The red striations remained, but they looked washed out. The coral was still inflating at night, which was a good sign, but the color loss was accelerating.

The fix, recommended by Renata after the subject emailed her photos, was to move the coral to the darkest corner of the tank — a spot under an overhang where the PAR reading was 35. “Put it somewhere you think is too dark,” she said. “If you can still see it without a flashlight, it’s too bright.” The subject moved the coral to a shaded area behind a large rock formation. The PAR there was 28. Within two weeks, the green began to return, starting from the center of the disk and working outward. The coral never fully recovered the intensity of its original color, but it stabilized at a medium green with visible red lines after about six weeks.

The lesson, which applies to any Scolymia acquisition, is to start the coral in the lowest light area of the tank and move it upward only after observing its response over several weeks. A coral that inflates fully at night and extends its feeding tentacles is ready for a slightly brighter spot. A coral that stays deflated or begins to pale is telling you the light is too high. There is no shortcut for this observation period.

Brown Film at the Base

Scolymia are aggressive feeders. They will capture and consume small fish, shrimp, and any pellet or frozen food that lands on their disk. The subject fed the coral a mixture of frozen mysis and Reef Roids twice a week, targeting the mouth with a pipette. The coral responded well to feeding, inflating noticeably within minutes of the food touching its surface.

The issue was water quality. The subject’s tank was young — eight months old — and the nutrient levels were unstable. Nitrate hovered around 15 ppm, phosphate at 0.12 ppm. Those numbers are fine for a mixed reef, but for a Scolymia that was already stressed from the lighting shock, they were not ideal. The coral’s tissue began to show signs of bacterial infection at the base, where the flesh meets the skeleton. A small, brownish film appeared on day twelve, spreading slowly over three days. The subject treated with a freshwater dip — a 60-second dip in tank-temperature RO water — which removed the film but also caused the coral to expel mucus heavily for two days afterward.

The better approach, learned from other keepers on a local forum, is to maintain nitrate between 5 and 10 ppm and phosphate below 0.08 ppm for the first month after introducing a Scolymia. Higher nutrients encourage bacterial growth on the coral’s surface, especially when the coral is already compromised. Lower nutrients starve the coral’s symbiotic algae at a time when the coral needs every source of energy it can get. The subject’s tank settled into that range after a series of smaller water changes — 10% every three days rather than 20% weekly — which minimized swings.

The Rippling Tissue Was a Warning

The subject’s tank had two Jebao OW-25 wave makers running at 70% power, creating a moderate, chaotic flow across the sand bed. The Scolymia’s tissue rippled in the current, which the subject initially interpreted as healthy. It was not. Within a week, the tissue on the side facing the flow had begun to erode, exposing a thin rim of skeleton. The coral was being physically abraded by the current, not killed by it, but the tissue loss was real and measurable.

The fix was to move the coral to a low-flow area behind a rock, where the water movement was barely perceptible. The tissue erosion stopped within three days. For Scolymia, the ideal flow is just enough to keep detritus from settling on the coral’s surface, but not enough to move the tissue itself. A good test: if the coral’s feeding tentacles cannot extend fully during feeding, the flow is too high. The subject now places Scolymia in areas where the flow is so low that a piece of floss dropped into the water takes several seconds to drift out of sight.

The Notebook Next to the Tank

There are specific, identifiable decisions that contributed to the color loss, and the subject has since documented them in a notebook that sits next to the tank. The list is short and specific:

• Acclimate for two hours minimum, not one. The extra time allows temperature and salinity to equalize slowly, and it gives the coral’s cells time to adjust without osmotic shock.
• Test the bag water for ammonia before starting. If levels are above 1.0 ppm, do a quick pre-dilution in a separate container with tank water before beginning the drip.
• Start the coral at PAR below 50. A shaded corner, under an overhang, or behind a rock. No exceptions for the first two weeks.
• Feed sparingly for the first week. The coral will take food, but the digestive demand adds stress. One small feeding on day four is enough.
• Watch the base of the coral, not the top. Tissue erosion starts at the skeleton-flesh interface, not on the exposed disk. If the base looks clean and white, the coral is stable. If it shows brown film or grayish discoloration, intervene immediately with a dip.
• Keep a log of PAR readings and coral response. The subject’s second Scolymia, acquired three months later, was placed at a measured PAR of 32. After ten days, it was moved to a spot reading 45. After another ten days, to 60. The color held throughout. The second coral remains deeper green and more extended than the first ever managed.

The original Scolymia sits in a low-flow corner under a shaded rock ledge, receiving 28 PAR for seven hours a day. It is not the striking green-and-red specimen that arrived in the box. It is a muted, pale green with faint red lines that are visible only under blue light. It inflates fully every night and accepts food when it is offered. It is alive, and it is stable, but the green at its center has not returned — and probably never will.