The Middle Kingdom: LPS

Large-polyp stony corals — LPS — are the middle kingdom of reef keeping, and for many people the most rewarding place to live. They have the fleshy, animated look of soft corals but the light-catching, structure-building nature of stony corals. They eat, they sway, they glow, and most of them are forgiving enough for a keeper who has a few months of experience and a testing habit.

If softies taught you to read a coral, LPS teach you to feed one and to respect its chemistry. This chapter covers the group, its needs, and the one thing that gets more LPS killed than anything else: warfare.

What LPS Are

LPS corals build a hard calcium carbonate skeleton like their small-polyp cousins, but they cover it in large, fleshy polyps that inflate with water and, in many species, extend long feeding tentacles. That flesh does two useful things for a keeper: it makes them tolerant of moderate rather than blinding light, because the tissue itself is doing some of the work, and it makes them visibly expressive, so you can read their mood at a glance.

Because they lay down real skeleton, LPS consume calcium and, more importantly, alkalinity. In a lightly stocked tank a few LPS will barely move your numbers, but as the collection grows, dosing becomes part of your routine. This is the group where testing stops being optional.

The Core LPS You Will Meet

Euphyllia: Hammers, Torches, and Frogspawn

The Euphyllia genus is the gateway drug of LPS: hammer corals with anvil-tipped tentacles, torch corals with long flowing tentacles and glowing tips, and frogspawn with clustered branching polyps. They want moderate light, moderate and gentle flow that lets the tentacles flow rather than whip, and space, because they carry long sweeper tentacles that sting anything within reach. Torches are the divas of the group — sensitive to change and to being pestered — while hammers and frogspawn are notably tougher.

Acanthastrea and Micromussa (Acans)

Acans are encrusting colonies of fat, candy-colored polyps that have become collector favorites. They want low to moderate light, gentle flow, and they respond dramatically to feeding — an acan target-fed regularly will grow and color up far faster than a starved one. They are ideal for the lower and middle rockwork.

Blastomussa, Duncans, and Candy Cane

This cluster of beginner-friendly LPS asks for very little: moderate-to-low light, gentle flow, and the occasional meal. Duncans in particular are among the toughest of all LPS and take food eagerly, making them a superb confidence-builder for a keeper trying feeding for the first time.

The Open-Brain and Plate Corals

Wellsophyllia and Trachyphyllia open brains, and Fungia plate corals, are sand-dwelling LPS that inflate into gorgeous fleshy domes. They belong on the sand bed, not the rock, in gentle flow, and they are hungry — heavy feeders that reward a target feed.

The Alkalinity Demand

Here is where LPS diverge from softies. Every gram of skeleton an LPS lays down draws calcium and carbonate from your water, and the carbonate side is measured as alkalinity, or dKH. As your LPS collection grows, alkalinity consumption becomes measurable, and if you do not replace it, your dKH drifts down and your corals suffer.

The rule that matters more than any target number is stability. LPS tolerate a range of alkalinity — anywhere from about 7 to 9 dKH is fine — but they hate a moving target. A swing from 8 to 11 and back over a few days does more damage than sitting steadily at either value. That is why you test. An alkalinity test kit is the single most-used tool in a reef keeper's cabinet, and running it a couple of times a week tells you whether your tank is starting to consume enough to need dosing. When you branch into multiple parameters, a broader reef master test kit covering calcium and magnesium alongside alkalinity keeps the whole skeleton budget in view. The full mechanics of dosing live in the chemistry handbook; here, the lesson is simply: test before you have a problem.

Coral Warfare and Sweeper Tentacles

LPS are not the peaceful residents they appear to be. Many, especially Euphyllia, deploy sweeper tentacles at night — long, translucent, heavily armed tentacles that reach several inches beyond the coral's daytime footprint to sting competitors. Two hammers touching may be fine, being closely related, but a torch reaching a distant acan can kill it over a few nights while you sleep.

The defense is spacing. Give LPS a generous no-mans-land — several inches of clear water around aggressive species — and remember that they grow, so today's safe gap is next year's border war. We map this out fully in the placement and warfare chapter, and for LPS it is the difference between a thriving reef and a slow-motion massacre.

Reading an LPS

An LPS tells you how it feels through inflation. A happy hammer or torch inflates fully, tentacles flowing. A stressed one stays deflated, retracts its tentacles, or shows receding tissue that exposes bare white skeleton at the base — tissue recession is the warning sign to act on. Common causes are too much flow, a chemistry swing, a sting from a neighbor, or a pest. When an LPS deflates, work through those in order rather than panicking.

Placing and Feeding LPS

LPS sit in the middle of the tank in more ways than one. Most want the moderate-light, moderate-flow real estate of the middle rockwork and the sand bed, below the SPS zone and above or beside the softies. Within that band, match the specific coral: Euphyllia and acans take moderate light and gentle flow, while sand-dwellers like open brains and plate corals belong on the bottom in the gentlest flow you have. Flow that is too strong is the most common LPS complaint — a hammer or torch that will not fully inflate is almost always sitting in too much current.

Feeding is where LPS reward you. Unlike most softies, many LPS actively capture food, and a target feed of meaty foods a couple of times a week visibly speeds their growth and deepens their color. Duncans, acans, and open brains in particular respond dramatically. Turn the flow down for a few minutes so the food is not blown away, place a small portion directly on the coral's polyps or extended feeder tentacles, and watch it draw the food in. Feed only what the coral actually takes, and match the extra input with nutrient export so you do not fuel algae.

Give every new LPS the same courtesy you give any coral: dip it, acclimate it low and slow to your light, and place it with room to grow and room for its sweeper tentacles to reach nothing. An LPS placed thoughtfully and fed occasionally is one of the most rewarding corals in the hobby — expressive, colorful, and forgiving enough to teach you the feeding and dosing habits that SPS will later demand. Learn to read an LPS the way you learned to read a softie, and it will tell you plainly whether it wants more food, less flow, or simply to be left alone to settle in.

FAQ

What is the difference between LPS and SPS corals?

LPS, large-polyp stony corals, have big fleshy polyps over their skeleton, tolerate moderate light and flow, and often eat readily — corals like hammers, torches, and acans. SPS, small-polyp stony corals, have tiny polyps over intricate skeletons, demand intense light and flow, and above all need rock-steady chemistry. LPS are the sensible step between soft corals and the demanding SPS.

Do I need to dose for LPS corals?

Not at first. A few LPS in a regularly water-changed tank usually get enough calcium and alkalinity from the water changes alone. As your stony coral load grows, their skeleton building consumes alkalinity and calcium faster than water changes replace it, and you will see your alkalinity drifting down on tests. That is your signal to begin dosing, which is why testing comes before dosing.

Why is my hammer or torch coral not opening?

A deflated Euphyllia is usually reacting to flow that is too strong, a recent parameter swing, a sting from a neighboring coral, or acclimation stress. Move it to gentler flow, confirm your alkalinity is stable, check that no other coral's sweeper tentacles can reach it, and give it several days undisturbed. Persistent recession of tissue off the skeleton means you need to act quickly to find the cause.