Montipora capricornis

Montipora capricornis, called simply "monti cap" in the hobby, is a plating small-polyp stony coral (SPS). The colony expands as thin, horizontal layers; the layers overlap or curl around themselves to form vase-like spirals. The surface carries tiny polyps that are hard to make out with the naked eye. In the trade, green, orange-red and purple forms are seen most often; the growth edge is usually a lighter color.

It is far more forgiving than Acropora and is one of the first species recommended to those who want to try stony corals after soft corals and LPS. Still, it needs stable KH, calcium and magnesium; it should be added not to a newly set-up aquarium but to a system that is at least a few months old and has settled into balance.

Like all stony corals (Scleractinia), its international trade is subject to CITES Appendix II. Choose an aquacultured frag or a farmed piece instead of a wild-collected colony; these are already used to aquarium light and water conditions.

It lives in the Indo-Pacific and the Red Sea, in the well-lit upper half of reefs, on slopes and along sheltered lagoon edges. Its plating shape serves to collect light over a wide surface, so it does well where light is somewhat reduced and flow is moderate. In the wild its layers overlap to build tiered structures that can spread over several meters.

• Light: Moderate light is enough; roughly 100–250 PAR gives good results. Red and purple forms color up more brightly as light increases. Keep a new piece under lower light first and move it up over two to three weeks.
• Flow: Moderate flow that changes direction. Because the plates act like sails, they can break in very strong, one-directional flow; if flow is weak, detritus settles on the surface.
• Placement: A ledge in the middle part of the rockwork where the plates can open out sideways. Do not place other light-demanding corals beneath it.
• Water parameters: Salinity 1.025–1.026, KH 7–9 dKH, calcium 400–450 mg/L, magnesium 1250–1400 mg/L. Keep nitrate around 2–10 mg/L and phosphate around 0.02–0.08 mg/L. It is not as sensitive as Acropora, but KH swinging by more than 1 dKH in a day can cause tissue loss from the edges.

It gets most of its energy from the symbiotic algae (zooxanthellae) in its tissue; no extra feeding is needed. It also uses fine particles and dissolved nutrients in the water, so nitrate and phosphate dropping completely to zero fades its color and slows growth. In most aquariums, leftover fish food provides enough nutrition.

It is not an aggressive coral; it has no stinging or long tentacles. Its real problem is that its rapidly expanding plates shade the corals below and beside it and grow toward whatever they touch. Leave about 10 cm of space around its edges. Keep it away from long-tentacled LPS such as Euphyllia and Galaxea; they easily sting its tissue.

Some dwarf angelfish and butterflyfish may pick at the polyps. Its most important pest is the Montipora-eating nudibranch (Phestilla subodiosa): these slugs, about 1 cm long and taking on the color of the coral, usually hide on the underside of the plates and also lay their white egg spirals there.

The plates are easy to cut: a 2–3 cm piece is broken off the edge with coral cutters and attached to a frag plug with gel cyanoacrylate glue. Within a few weeks the piece attaches to the plug and puts out new plates; the cut edge of the mother colony also heals quickly. Keep the frags under light similar to the mother colony and in steady flow.

• Bite marks, white patches on the plates: First check the underside of the plates with a flashlight; the nudibranchs and their eggs are usually there. Put every newly arrived Montipora through a coral dip and keep it under observation for a few weeks.
• Tissue loss (STN/RTN): Tissue receding slowly (STN) or rapidly within days (RTN) from the base or the edges is usually caused by KH or temperature swings, sometimes by a bacterial infection. Stabilize the water parameters first; if the loss progresses, cut off the healthy part and save it as a separate frag.
• Browning or fading: Browning points to low light or high nutrients, whitening to too much light.