Psammocora Coral Care: Light, Flow, Color and ID

You glue a small psammocora frag to the rock and forget about it. Two months later it has crawled off the plug and across the rock in a thin, fuzzy sheet, and someone at the club asks if that is a montipora. It is not. Most people who own one have had to explain that at least once.

Psammocora is a small-polyp stony coral from the Indo-Pacific. Most of what you see for sale grows as a crust that spreads over rock, with a velvety surface of tiny polyps. It is one of the easier stony corals to keep. The two things that trip people up are telling it apart from look-alikes and giving it enough flow to keep that fuzzy surface clean.

What psammocora is, and the spelling problem

The name comes from the Greek word for sand, and older common names follow the same idea: sandpaper coral and cat’s paw coral. You will also see it spelled “psammacora,” including on our own Orange listing. Both spellings point to the same coral. Psammocora is the correct one.

It has an unusual family tree. For years it was filed in the family Siderastreidae with the starlet corals. DNA work showed that was wrong, and it now sits in its own family, Psammocoridae, where it is the only genus. About eight species are recognized. That is part of why the trade names tell you so little: “Orange” and “Watermelon” are color selections, and our listings say the name describes the aquarium strain, not a confirmed species.

How to tell it from montipora and other encrusters

Psammocora gets confused with encrusting montipora, leptastrea, pavona and leptoseris, and growers who culture it say vendors mislabel it often. Look at the surface up close with a flashlight.

Coral	What the surface looks like
Psammocora	Very small polyps, no more than about 1/8 inch across, sitting in shallow pits with no distinct walls between them. Reads as fuzzy or sandy. Polyps are usually out in the daytime.
Encrusting montipora	Tiny polyps spread over a surface that often has small bumps or ridges between them. Usually a thinner, smoother plate.
Leptastrea	Larger, clearly separate cups packed against each other, often with a contrasting center color.
Pavona and leptoseris	Polyps lined up along ridges or radiating lines, sometimes forming plates or fronds.

Our coral identification guide covers more of the look-alikes, and the encrusting corals page shows the whole group.

Encrusting vs branching forms

Psammocora grows encrusting, massive, branching or in columns, depending on the species. The pieces in the trade, including ours, are almost all encrusting. They spread outward as a sheet first and later build up into bumps and knobs. Branching species like Psammocora contigua form flattened branches and nodules and are described as slow growers. The encrusting forms are a different story. They are known for covering rock fast for a stony coral, and some reefers use them as living ground cover in SPS tanks.

That speed is useful and it is also the main thing to plan for. An encruster does not stop at the edge of its rock. Mount it where you want it to spread, and keep it off the frag rack or egg crate you do not want covered.

Light and flow numbers

Our listings run psammocora at medium light, 100 to 200 PAR, with medium flow. The overgrown WYSIWYG frags are listed up to 250 PAR. Growers who culture a lot of it start around 100 to 200 PAR and report that colonies kept under about 50 PAR lose their brightness. Start a new piece toward the low end and move it up over a week or two. Too much light too fast bleaches it quicker than too little light hurts it.

Flow is where people go wrong. The fuzzy surface traps detritus, and tissue under a film of debris dies in patches. Aim for medium to strong, changing flow that crosses the coral instead of a single jet pointed at it. If you see a gray film or a bare patch in a low spot, flow is the first thing to check. Clean your pumps too. Flow drops slowly as pumps foul, and the coral notices before you do.

Color: why it holds steady

Wild psammocora is mostly cream, brown or gray. The orange, watermelon and blue pieces in the hobby are selected color morphs. The good news is that psammocora color tends to stay fairly consistent. It does not swing as hard as acropora or montipora when your nutrients or light shift a little.

When it does fade, the cause is usually one of three things: light too low (it browns), light too high or raised too fast (it pales), or nitrate and phosphate bottomed out (it goes pale and thin). Corals need some nitrate and phosphate to feed. Our reef tank water parameters guide lists the ranges, and zooxanthellae explained covers why a coral turns brown under low light.

Feeding

Psammocora is photosynthetic and gets most of what it needs from light. The polyps are too small for spot feeding, but they catch fine particles well. Our listings call it low on feeding, with optional amino acids or very fine foods used sparingly. If you want to feed, broadcast a fine food such as rotifers or a reef powder once or twice a week with the pumps turned down for a few minutes. Heavy feeding raises nutrients and coats the surface, which does more harm than good. Our coral feeding guide covers amino acids in more detail.

Aggression and spacing

Psammocora has no long sweeper tentacles, and our listings call it peaceful. It still competes. Any coral that grows into another will fight at the contact line, and an encruster wins most of those fights by growing over its neighbor. Give it 2 to 3 inches from other corals, more from fleshy LPS, and keep it well away from known bullies like hydnophora, which will burn it. A rock of its own is the easiest way to let it spread without trimming.

Common problems

What you see	Likely cause	What to do
Bare or gray patches in low spots	Detritus settling on the surface	More crossing flow, clean the pumps
Pale or white all over	Too much light too fast	Lower it or dim the light, then raise slowly
Dull brown	Too little light or high nutrients	More light, keep nitrate and phosphate low but not zero
Tissue pulling back from the edge	Alkalinity swings or contact with a neighbor	Test alkalinity, check what it is touching. See bleaching vs STN vs RTN
Covering a rack or the glass	Normal growth	Trim the edge, or frag it onto plugs

Fragging

Encrusting psammocora is easy to propagate. You can cut a section off the growing edge with a saw or bone cutters and glue it to a plug. Or set a plug against the growing edge and let the coral crawl onto it, then snap it free. Wear gloves when you cut.

Acclimation

Corals do not need a drip. Turn the lights off and float the sealed bag for 15 to 20 minutes. Open it into a clean container and add about half a cup of tank water every few minutes for 15 to 30 minutes. Lift the coral out by its plug and throw the bag water away. Dip it before it goes in the display, then place it low in the tank with the light off or low for the first day.

FAQ

The Underwater Gardener is a reef aquarium store in Key West, Florida. Quarantined: held at our Key West facility for at least 4 weeks and dipped multiple times before it’s offered for sale. Livestock ships UPS Next Day Air on Tuesdays and Wednesdays.