Coral care, demystified: soft, LPS, and SPS — what each group actually needs

The soft / LPS / SPS taxonomy isn't really about biology. It's a hobbyist shorthand for how much light, flow, and chemistry stability a coral demands. A reef tank you read as "beginner" is just a tank full of corals that tolerate forgiving conditions. The hard part is moving up the ladder without killing what you already have.

This guide covers what each group is, what they actually need, and how to sequence your first corals.

Soft corals — the gateway

What they are: Corals without a hard calcium-carbonate skeleton. They flex and sway. The everyday names: zoanthids and palythoas ("zoas"), mushrooms (discosoma, ricordea), green star polyps (GSP), leather corals (toadstool, finger leather), Kenya tree, pulsing xenia.

Light: Low to medium. 50–150 PAR at coral height. Most softies tolerate a wide range; many burn under SPS-grade lighting.

Flow: Low to medium. They like gentle, variable flow. Direct blast from a powerhead will collapse a leather or shred xenia.

Chemistry: The most forgiving group in the hobby. They don't deposit calcium carbonate, so alkalinity swings of 1–2 dKH won't faze them. Salinity drift, slightly elevated nitrate (5–15 ppm), and skipped water changes are mostly survivable.

Placement: Lower-to-mid rockwork, away from direct flow. Some softies (Kenya tree, GSP, xenia) are aggressive growers — give them their own rock or expect them to take over.

Beginner-friendly because: they survive the chemistry mistakes new reefers make. Most don't need supplemental feeding. Frags are cheap ($10–25).

LPS — the middle tier

What they are: Large Polyp Stony corals — hard skeletons with chunky, fleshy polyps. The hobby names: hammer, frogspawn, torch (all in the Euphyllia family), candy cane (caulastraea), duncan (duncanopsammia), plate coral (fungia, cycloseris), open brain (trachyphyllia, lobophyllia), acan (micromussa), blastomussa.

Light: Medium. 75–200 PAR. Most LPS scorch under SPS lighting and will retract or bleach. The lower end of the range suits Goniopora, elegance, and other lower-light LPS.

Flow: Low to medium, variable. Steady direct flow stresses fleshy LPS — alternating gyre patterns are better. Torches and frogspawns have stinging sweeper tentacles that extend 4–6 inches at night; leave space.

Chemistry: Tighter than softies. Alkalinity 8–11 dKH, stable. Calcium 400–450 ppm. Magnesium 1300–1400 ppm. Most LPS are photosynthetic but feed enthusiastically on meaty foods (mysis, reef roids, small bits of silverside) — feeding 1–2× per week dramatically improves color and growth.

Placement: Lower-to-mid third of the tank. Leave a 4–6 inch perimeter around euphyllia to avoid sting wars with other corals.

The right "second coral" purchase. Once your tank is 4–6 months old with stable parameters and you've kept softies alive, a hammer or frogspawn is a satisfying jump up. They have presence — the fleshy polyps move in the flow in a way softies don't.

SPS — the demanding tier

What they are: Small Polyp Stony corals. Hard skeletons with tiny polyps that give them a textured, branching appearance. The hobby names: acropora ("acro"), montipora (digitata, capricornis, encrusting), stylophora, pocillopora, seriatopora ("birdsnest").

Light: High. 200–400+ PAR for acropora. Montiporas are more forgiving (150–250). Bleaching from excessive light happens fast — frags must be acclimated by starting low in the tank and walking them up over 2–3 weeks.

Flow: High and turbulent. SPS need flow to deliver nutrients, sweep away waste, and prevent algae from settling on tissue. Tanks with successful acropora typically run 30–50× tank turnover via gyre or vortex powerheads. Dead spots = STN (slow tissue necrosis).

Chemistry: Unforgiving. Alkalinity needs to be stable (pick a number 7.5–10 dKH and hold it within 0.5 dKH). Calcium 400–450 ppm. Magnesium 1300–1450 ppm. Nitrate 1–10 ppm (not zero — ULNS tanks bleach corals). Phosphate 0.03–0.10 ppm. Salinity 1.025–1.026 ppm, no drift.

Alkalinity swings are the #1 SPS killer. A 2 dKH jump in 24 hours can trigger RTN (rapid tissue necrosis) — you watch tissue slough off in a day. Most SPS keepers run automated 2-part or calcium reactor dosing to hold parameters within ±0.2 dKH.

Placement: Upper third of the tank for acropora, mid-to-upper for montipora and stylophora. Plenty of space — SPS encrust and branch outward.

Why people fail at SPS: they buy them too early. A 6-month-old tank with unstable alk will lose every acro frag in it. SPS is a discipline tax on the rest of your reefkeeping.

What changes as you climb the ladder

What new keepers get wrong

1. Jumping to SPS in month three. The tank physically can't hold alkalinity stable yet because the live rock is still cycling, bacterial populations are fluctuating, and you haven't built the dosing routine yet. Wait.

2. Mixing high-touch softies with SPS in the same tank. Pulsing xenia, GSP, and leather corals release terpenoid compounds (allelopathy) that suppress SPS growth. If you want a serious SPS tank, restrict softies to the sump or skip them entirely.

3. Inadequate flow for SPS. Most beginner tanks run 10–15× turnover. SPS wants 30–50×. The fix is more or bigger powerheads, not larger return pumps.

4. Acclimating frags to light too aggressively. A new acro frag from a vendor's holding tank may have been under 100 PAR. Dropping it under your 350 PAR top-rock spot bleaches it in 48 hours. Always start frags low in the tank and walk them up 1–2 inches per week.

5. Reading "reef safe" labels as binary. Some fish (tangs, clowns, basslets) will nibble on LPS or SPS but not softies. Some (angels, large wrasses) sample anything. Cross-reference our species database for each fish you keep.

A practical first-coral roadmap

Month 4–6: Start with 2–3 hardy softies — a zoanthid colony, a green star polyp frag on its own rock, one mushroom. Place mid-tank, low flow. Don't add anything else for a month. Watch how your alkalinity tracks.

Month 6–9: Add your first LPS — a hammer frag or candy cane. Test alk weekly; if it stays within 1 dKH on its own, you're ready for more. Add a frogspawn, an acan, maybe a duncan.

Month 9–12: Your tank is now consuming enough alk/calcium that you need to dose. Set up 2-part dosing or kalkwasser. Once you've held alkalinity within 0.5 dKH for two months on auto-dose, consider your first SPS — a montipora capricornis frag is the easiest start.

Month 12+: Acropora is on the table. Start with a hardy strain (green slimer, tricolor valida) before getting into the boutique frags. Place mid-height, walk it up.

Patience is the only differentiator between hobbyists who keep SPS long-term and those who don't. The tank you build slowly survives.