Soft Corals (Leather, Mushroom, Toadstool): A Starter List

If a hammer coral is the gateway to LPS, a toadstool leather is the gateway to keeping any coral alive. Soft corals are the forgiving tier of the hobby: no skeleton to calcify, no PAR meter required, no alkalinity swing that ends in a bleaching event. They photosynthesize through their zooxanthellae, tolerate the nutrients that LPS and SPS hate, and a single frag will often double in size within three to four months of a stable tank. My own 90-gallon soft-coral-dominant mixed reef has run for nine years on the same eight colonies and it is the tank I point every beginner toward first.

What "Soft Coral" Actually Means (and the Three Families You'll Buy)

The term "soft coral" covers roughly 50 genera in the order Alcyonacea, but in the trade you will meet the same three families over and over. They share a single defining trait: no aragonite skeleton. Instead of building a calcium carbonate cup, they grow on a flexible, leathery base that sways with the current. That single biological decision is what makes them tolerant of the parameter swings that kill SPS.

The three families I recommend to every new reefer:

• Toadstool leathers — Sarcophyton glaucum and S. ehrenbergi. The cap-shaped, mushroom-on-a-stalk silhouette most hobbyists picture when they hear "leather coral." They grow fast, shed a waxy cuticle every 4–6 weeks, and tolerate the widest range of light and flow of any coral in the trade.

• Finger / flexible leathers — Sinularia and Lobophytum. Branching or finger-like colonies that sway in flow like a field of wheat. They are the most chemical-warfare-prone corals on this list, so placement matters.

• Mushroom corals — Discosoma, Rhodactis, and the showpiece Ricordea florida. Disc-shaped polyps with a fluorescent mouth, no stalk, no branching. They are the lowest-light, lowest-flow, lowest-maintenance coral you can buy — a Rhodactis will thrive under a PAR of 30 and survive a missed water change without complaint.

A fourth group — zoanthids and palythoas — shows up in every starter list, but I treat them as a separate category because of the palytoxin warning (see closing).

Water Parameters and the Chemistry That Drives Growth

Soft corals do not calcify, so the calcium and alkalinity numbers that govern LPS and SPS are far less critical. What they do need is a stable ionic environment for their tissue to maintain turgor, and a low-but-not-zero nutrient load to feed on. Here are the targets I run:

| Parameter | Target | Acceptable swing | Test frequency |

|---|---|---|---|

| Alkalinity (dKH) | 8.5 | ±0.5 dKH / week | Weekly |

| Calcium (ppm) | 420 | ±20 ppm / week | Weekly |

| Magnesium (ppm) | 1,300 | ±100 ppm / week | Weekly |

| Nitrate (ppm) | 5–15 | 2–25 | Weekly |

| Phosphate (ppm) | 0.05–0.15 | 0.02–0.20 | Weekly |

| Salinity (sg) | 1.025 | ±0.001 | Daily (refractometer) |

| Temperature (°F) | 78 | 76–80 | Continuous probe |

The reason soft corals prefer nitrate and phosphate above the ultra-low values SPS hobbyists chase is simple: they feed on dissolved organics. Their tissue absorbs nitrate, phosphate, and amino acids directly from the water column through a process called heterotrophic absorption. The rule of thumb is that nitrate below 2 ppm starves mushroom corals and slows leather growth; nitrate above 25 ppm causes the dreaded "brown jelly" bacterial blooms on leathers. Keep it in the middle and they thrive.

The chemistry formula that matters here is the Redfield ratio for coral tissue:

**C : N : P = 106 : 16 : 1** (molar)

In practical reef terms, this means a nitrate of 10 ppm NO₃-N and a phosphate of 0.6 ppm PO₄-P (molar) keeps soft-coral tissue in balance. If phosphate creeps above 0.20 ppm and nitrate stays at 5 ppm, the Redfield ratio is broken and you will see cyanobacteria blooms on the leathers' bases. If the ratio inverts (low phosphate, high nitrate), the mushrooms will starve and the toadstool will not grow.

For testing, I use the Hanna HI713 (phosphate) and HI707 (nitrate) colorimeters weekly, plus the HI772 alkalinity checker for spot checks. Skip the API test strips — the color steps are too coarse for the ±0.5 dKH tolerance I want.

Lighting, Flow, and PAR Targets

Soft corals evolved in shallow reef flats and shaded overhangs, often in turbid water. They want less light than LPS and far less than SPS. The PAR targets I use:

• Toadstool leathers (Sarcophyton): 60–120 PAR at the cap.

• Finger leathers (Sinularia, Lobophytum): 80–150 PAR at the colony.

• Mushroom corals (Discosoma, Rhodactis, Ricordea): 30–80 PAR at the disc.

If a mushroom coral is placed under 200 PAR it will retract and bleach in two to three weeks. If a toadstool is placed under 30 PAR it will survive but stop growing and stretch its stalk toward the surface trying to catch more light. Hit the middle of the band and the colony will be fully expanded, brightly colored, and visibly polyped-out within a month.

The fixtures I run on my own 90-gallon soft-coral tank are two AI Hydra 32HD set to 70 % intensity with the "Reef White" spectrum, photoperiod 9 hours on, 15 off, with a 90-minute ramp at each end. For a budget setup, a pair of Nicrew HyperReef 100W LED bars at the same intensity and photoperiod will grow leathers and mushrooms equally well.

Flow is the more important variable for leathers. They want moderate, indirect, alternating flow — enough to keep detritus from settling on the cap, not enough to bend the polyps flat. A single Tunze 6095 wavemaker on pulse mode at 40–60 % intensity is correct for a 4-foot tank. Mushrooms want less: position them on a shaded ledge or in a corner with almost no direct flow.

Placement, Aggression, and the Chemical Warfare Problem

This is the section I wish someone had written for me in my first year. Soft corals do not sting like LPS — they have no sweepers — but they fight a different war. Leather corals, especially Sinularia and Sarcophyton, release terpenoid compounds into the water to inhibit the growth of neighboring corals. In a 90-gallon tank with one or two leathers this is invisible. In a tank with five or six leathers crammed together it can stunt every coral in the system.

The rule I follow:

• 5–7 inches (12–18 cm) between leather colonies.

• 8–10 inches (20–25 cm) between any leather and any LPS or SPS.

• Run carbon — a Rox 0.8 or Two Little Fishies PhosBan reactor with MatrixCarbon changed every 4 weeks — to strip the terpenoids before they accumulate.

• Run a protein skimmer — even on a "softie" tank. A Red Sea Reefer G2 or IceCap K1-160 sized to the tank will pull the dissolved organics the leathers would otherwise absorb and re-release as terpene precursors.

Mushroom corals are the opposite. They are essentially non-aggressive and do not chemically compete. They will, however, slowly walk across the rockwork on their disc foot, and a fast-growing Rhodactis can smother a small zoanthid colony within six months. Position mushrooms on isolated islands of rubble so they cannot reach more expensive neighbors.

A 30-Gallon Soft Coral Starter Kit (Brands and Models)

For a first soft-coral tank, this is the kit I would buy in 2026. It is the same kit I would have recommended in 2018 — soft corals do not need the latest gear, just stable gear.

• Tank: Waterbox AIO 30.2 or Red Sea Reefer 350 (if budget allows the 100-gallon-plus range, the stability is better).

• Lighting: AI Hydra 32HD (one for the 30.2) or Radion XR15 for the 100 gal.

• Flow: Tunze 6095 wavemaker (one for the 30.2, two for the 100 gal).

• ATO: Tunze Osmolator 3155 — every reef needs one, soft corals included.

• Skimmer: IceCap K1-160 (tanks up to 75 gal).

• Return pump: Ecotech Vectra M2 with a small APC UPS battery backup.

• Controller: Neptune Apex with the PM1 expansion module for monitoring (dosing is optional on a soft-coral tank — I dose only if alkalinity drifts below 7.5 dKH).

• Carbon and GFO: Two Little Fishies PhosBan reactor with MatrixCarbon, changed monthly.

• Test kit: Hanna HI97115 photometer (alkalinity + calcium + magnesium).

• Coral dip: Tropic Marin Pro-Coral Cure for every new frag before it enters the display.

A 30-gallon soft-coral tank running this kit on a stable weekly routine — 10 % water change with Tropic Marin Pro-Reef salt, carbon change, glass cleaning, parameter log — will keep every leather, toadstool, and mushroom alive and growing for a decade or longer.

Closing Thoughts and One Safety Warning

Soft corals are where I send every new reefkeeper. They reward consistency over precision and tolerate the rookie mistakes that kill SPS. The two disciplines that matter most: (1) keep nitrate above 5 ppm and below 25 ppm so the Redfield ratio stays balanced, and (2) run carbon and a skimmer to strip the terpenoids that leathers release.

One safety note: the zoanthid and palythoa family is sometimes lumped with "soft corals," and several species — especially Palythoa — contain palytoxin, one of the most potent non-protein toxins known. Never handle a zoanthid colony with bare hands in an enclosed room, never boil rocks to clean them (the aerosolized toxin has sent hobbyists to the hospital), and wear gloves and eye protection if you frag them. Leathers and mushrooms do not produce palytoxin and are safe to handle with bare wet hands.

Start with one toadstool, two mushrooms, and one finger leather. Give them a year. You will end up with six colonies and a hobby that lasts a lifetime.