LPS Corals (Brain, Hammer, Torch): Husbandry Essentials
If you have ever walked past a reef tank and watched a hammer coral pulse its tentacles like a field of tiny anchors, you already understand why LPS — large polyp stony corals — are the gateway genus for almost every reefkeeper. They are forgiving, photogenic, and forgiving enough that beginners can succeed with them in their first six months. But "forgiving" is not the same as "indifferent." LPS corals still calcify, still feed, and still punish a hobbyist who lets alkalinity swing by more than 1.5 dKH in a week. This guide is the protocol I run in my own 220-gallon mixed reef and recommend to clients.
What Qualifies as an LPS Coral (and the Three Families You'll Actually Buy)
The "LPS" bucket is a hobby term, not a scientific one. It groups together any stony coral whose polyps are large enough to see with the naked eye, and whose flesh completely retracts over the skeleton at night. In practical terms, that means three families dominate the trade:
- Brain corals — Favia, Favites, Platygyra, Caulastrea (trumpet/candy cane), and the showpiece Trachyphyllia (open brain / Wellsophyllia). Skeleton is solid, polyps are fleshy, sweeper tentacles are short.
- Hammer corals — Euphyllia ancora. Anchor-shaped tentacle tips, branching skeleton, very long sweeper tentacles at night (often 4–6 inches / 10–15 cm).
- Torch corals — Euphyllia glabrescens (and the closely related E. divisa / frogspawn, which most shops lump in). Tentacle tips have a rounded, ball-shaped "torch" instead of an anchor.
All three share the same basic biology: they host zooxanthellae for photosynthesis, they capture zooplankton, and they build a calcium carbonate skeleton using aragonite. That means the same four numbers govern their health in every tank: alkalinity, calcium, magnesium, and salinity.
The Non-Negotiable Water Parameters
If you take one thing from this article, take this table. These are the targets I aim for, the swing I tolerate, and the test cadence I use to stay inside those bands.
| Parameter | Target | Acceptable swing | Test frequency |
|---|---|---|---|
| Alkalinity (dKH) | 9.0 | ±0.3 dKH / week | 2× weekly |
| Calcium (ppm) | 430 | ±10 ppm / week | 2× weekly |
| Magnesium (ppm) | 1,350 | ±50 ppm / week | Weekly |
| Nitrate (ppm) | 5–10 | 2–20 | Weekly |
| Phosphate (ppm) | 0.05 | 0.02–0.10 | Weekly |
| Salinity (sg) | 1.026 | ±0.001 | Daily (refractometer) |
| Temperature (°F) | 77 | 75–79 | Continuous probe |
The relationship between alkalinity, calcium, and magnesium is governed by ion balance. Randy Holmes-Farley published the rule of thumb every reefer should memorize: for every 2.5 dKH of alkalinity consumed, roughly 18 ppm of calcium is also consumed, in roughly a 1:7 Ca:Alk molar ratio. That means if your alkalinity drops 1.0 dKH in a week, expect calcium to drop about 7 ppm. If you are dosing to fix one, you almost always need to fix the other.
Magnesium's job is to keep calcium and carbonate from crashing out of solution. The formula that matters is:
**Ca²⁺ × CO₃²⁻ < Ksp(magnesium-stabilized)**
Practically: keep Mg at 1,300–1,400 ppm and you stop worrying about precipitation. Below 1,200 ppm, calcium and alkalinity will fall together as they precipitate onto heaters, pumps, and the glass.
For testing, I use a Hanna Instruments HI772 (alkalinity) and HI758 (calcium) for daily spot checks, with a Tropic Marin ICP-OES lab kit sent quarterly to catch the trace elements (strontium, iodine, potassium) you cannot read with hobby kits.
Lighting: PAR Targets and Acclimation
LPS corals evolved in 20–40 ft (6–12 m) of water, often partially shaded by overhangs. They want moderate light, not the 400+ PAR blast that SPS corals thrive under.
- Brain corals: 80–120 PAR at the colony.
- Hammer and torch: 100–150 PAR at the polyp.
Higher PAR will not kill them outright, but it will bleach them within 2–3 weeks and they will not recover the lost color. Lower PAR is safer — you will just get slower growth and a stretched, "reaching" skeleton if you go too low.
If you are moving a frag up into brighter light, drop intensity by 30 % for the first two weeks, or place the colony on a shaded ledge and migrate it up over a month. AquaIllumination Hydra 32HD and Ecotech Marine Radion XR15 are my go-to fixtures for LPS-dominant tanks because their spectrum and PAR curves are well-documented. If you do not own a PAR meter, buy one — the Apogee MQ-510 pays for itself in saved corals.
Flow: The "Wiggle, Not the Wave" Rule
The mistake I see most often is LPS in a flow that pushes their polyps flat. A hammer coral with its tentacles streaming horizontally is not "happy and active" — it is being sandblasted. LPS need low-to-moderate, indirect, alternating flow.
The rule I tell every client: wiggle, not the wave. The polyps should sway gently with their tentacles still pointing upward. If the tentacle tips are whipping, the flow is too strong. If they are completely still, the colony is not getting enough gas exchange and detritus will accumulate in the folds.
For a 4-foot tank, one Tunze 6095 or Maxspect Gyre XF 330 set to 30–50 % pulse mode will outperform three powerheads cranked to full. Direct the flow at the glass opposite the coral so it bounces, not at the coral itself.
Feeding: When, What, and How Often
LPS corals are not photosynthetic only — they are voracious predators. A weekly feed does more for growth and color than any lighting or parameter tweak.
- Target foods: frozen mysis shrimp (PE Mysis, Hikari), brine shrimp for small polyps, and reef-roids slurry for broadcast feeders like Caulastrea. Chop mysis in half for hammer and torch polyps.
- Frequency: 1–2× per week for established colonies; every other day for new frags trying to grow.
- Time of day: 30 minutes after lights-out, when polyps are fully extended.
- Method: use a Julian Sprung feeding tube or a 1 mL syringe with airline tubing to deliver food directly to the mouth. Turn off return pumps and skimmer for 15 minutes so the food stays in the polyp.
A brain coral will completely engulf a single mysis in 20–30 seconds. A hammer polyp will hold food for 5–10 minutes as it digests. If a polyp rejects food within a minute, the coral is stressed — check parameters before feeding again.
Common Problems and How to Read Them
Even with perfect parameters, LPS will tell you when something is wrong. Here is the decoder:
- Polyp closed for >48 h: parameter swing, predator (peppermint shrimp, bristleworm), or a chemical war with another coral 6–10 in away. Hammer and torch corals can extend sweepers 8 in (20 cm) at night and sting neighbors badly.
- Skeleton exposed, flesh receding: too much flow or too much light. Move the colony, do not increase feeding.
- Brown jelly disease: a bacterial infection that turns tissue into a slimy brown mass. Cut it out with sharp scissors, dip the colony in a Tropic Marin Coral Dip for 5 minutes, and isolate in a hospital tank. Survival rate is 30–50 % if you catch it in 24 hours.
- Bleaching (white polyps, transparent tissue): alk swing >2 dKH, lighting shock, or a temperature spike >82 °F (28 °C). Reverse the cause; the coral will usually re-zooxanthellae in 6–10 weeks.
A Starter Shopping List (Brands and Models)
For a new LPS-dominant 60-gallon tank, this is the kit I would buy:
- Test kit: Hanna HI97115 (alkalinity + calcium + magnesium, three-in-one photometer)
- ATO: Neptune Systems ATK (auto top-off) or Tunze Osmolator 3155
- Skimmer: Red Sea Reefer G2 or IceCap K1-160 for tanks up to 75 gal
- Return pump: Ecotech Vectra M2 with battery backup
- Controller: Neptune Apex with PM1 and PM2 modules for dosing two-part (BRS Bulk Alkalinity + BRS Bulk Calcium)
- Two-part dosing: Tropic Marin KH/Alk Balance and Tropic Marin Ca/Mg Balance if you want pre-mixed, or BRS 2-Part Pharma for the value route
- Coral dip: Tropic Marin Pro-Coral Cure or Two Little Fishies Revive
A 60-gallon LPS tank running this kit on a stable dosing schedule will keep alkalinity within ±0.2 dKH week-over-week, which is the single biggest predictor of long-term LPS health.
Closing Thoughts
LPS corals are where I send every new reefkeeper — they reward good husbandry fast, they are dramatic, and they recover from mistakes more readily than SPS. The discipline you build around keeping a hammer coral stable is the same discipline that will let you graduate to Acropora three years from now. Hold alkalinity, hold calcium, keep magnesium out of the basement, feed them once a week after lights-out, and they will outlive your tank.
