A guide to growing corals: soft, LPS and SPS

Every coral you'll ever keep comes down to three things, and almost every coral death traces back to one of them. Light feeds the coral, because the algae living in their tissue (called zooxanthellae) photosynthesize and feed the host. Flow brings them food and oxygen and carries away waste so they don't sit in their own gunk. And stable water chemistry keeps them building skeleton instead of stressing.

The word that matters most is stable. Corals would rather have steady, slightly imperfect water than water that's perfect on Tuesday and swinging on Thursday. A salinity of 1.025 that never moves beats a 1.026 that drifts to 1.023 every week. This is the single biggest mindset shift from fish-only keeping.

As you climb the ladder, the demands on all three levers go up and your room for error goes down. Soft corals forgive a lot. SPS forgive almost nothing. Where you are on that ladder should match how dialed-in your tank and your habits are, not how cool the coral looks at the store.

Soft corals don't build a hard skeleton, and most of them are hard to kill. This is where everyone should start. The classic beginner group is mushroom corals (discosoma and rhodactis), zoanthids and palythoas ('zoas' and 'palys'), green star polyps (GSP), and leather corals (toadstool, kenya tree). They tolerate lower light, gentler flow, and water that isn't dialed in to the decimal.

Put them low-to-mid in the tank to start, in moderate, indirect flow. They don't need you to dose anything special and they don't need target feeding to survive, though many will respond to it. If a coral can teach you to read your tank without punishing you, it's one of these.

Two honest warnings. GSP and some leathers spread aggressively and take over rock, so give them their own island. And palytoxin in zoas and palys is a real thing: don't handle them with open cuts, never boil rock with them on it, and wear gloves and eye protection if you're fragging. Worth knowing, not worth being scared of.

Once soft corals are thriving and your parameters have held steady for a couple of months, step up to LPS. These build a calcium-carbonate skeleton with big fleshy polyps: hammers, frogspawn, and torches (the euphyllia family), candy cane (caulastrea), duncans, acans, and favia or brain corals. They want moderate light and moderate, gentle flow. Blast a torch with a powerhead and it'll never open.

This is the level where feeding starts to matter. LPS have real feeding tentacles and respond well to small meaty foods (mysis, finely chopped seafood, or a prepared coral food) target-fed a couple of times a week. They'll live off light alone, but they grow and color up faster when fed.

Because LPS build skeleton, they start pulling calcium, alkalinity, and magnesium out of your water. In a lightly stocked tank, weekly water changes often keep up. As you add more, you'll need to test and possibly dose those three. This is the moment to read our reef chemistry section below and get in the habit of testing.

SPS are the corals people picture when they imagine a reef: acropora, montipora, birdsnest, stylophora. They're also the ones that demand the most. With one fair exception: encrusting and plating montipora (montipora capricornis especially) are a lot more forgiving of light and nutrient swings than acropora, and many reefers treat them as the SPS entry point. Acropora is the coral to hold off on until your tank has been rock-stable for many months and you're comfortable testing and dosing. There's no shame in never going there. Plenty of beautiful, mature reefs are all soft coral and LPS.

SPS want three things at high intensity: high PAR (strong light, placed up high in the tank), high turbulent flow (they need water ripping past them to stay clean and fed), and pristine, rock-steady chemistry. Nutrients should be low but not zero, and your alkalinity, calcium, and magnesium need to stay in a tight band day to day. With acropora especially, even a 1 to 2 dKH swing in a single day can stress them and dull their color, and a fast crash of several points is often what browns out or kills a colony outright. The goal is to hold alkalinity within roughly half a point to a point over the course of a day, not to chase a perfect number.

At this level a calcium reactor or a doser usually replaces water changes as your way of keeping the big three steady, and you're testing alkalinity often, sometimes daily. If you're reaching for SPS, see our saltwater sump guide for the 125-gallon reef, because the equipment room is where these tanks are actually won.

Here's the one that kills more new corals than pests: people buy a coral grown under one light, bring it home, and drop it right under their own lights at full blast. The coral bleaches or browns out within days, and they think they did something wrong with their water.

Corals adapt their tissue to a given light intensity, and they don't switch fast. When you add a new coral, start it lower in the tank and run your lights at reduced intensity, then raise the coral or the light gradually over two to three weeks. If you have a programmable light, dialing the intensity up slowly is the cleaner way to do it.

Let the coral tell you when to stop, not a schedule. Pale or bleaching tissue means too much light too fast. Polyps staying closed or stretching way out reaching for light can mean too little. Move things an inch at a time and give it a few days to respond before you judge.

Corals are animals, and a lot of them fight for space. The most common surprise for new reefers is the sweeper tentacle: long stinging tentacles that some corals (euphyllia like hammers and torches especially) extend at night to sting whatever's downstream of them. You'll place two corals six inches apart, and a week later one is melting on the side facing the other.

The rule of thumb is to give corals room and watch the flow direction, since flow carries those tentacles and the chemicals some softies put out. Torches and frogspawn are some of the worst offenders. Many leathers wage chemical warfare instead, releasing compounds that stunt their neighbors, which is one more reason good flow and carbon help.

When in doubt, leave more space than looks necessary and rearrange while colonies are small. It's a lot easier to move a frag than to save a colony that's been getting stung for a week.

Coral pests ride in on the coral or even the frag plug: acropora-specific red bugs, montipora-eating nudibranchs, acro-eating flatworms, zoa-eating nudibranchs and sundial snails, plus aiptasia or bubble algae hitchhiking on the rock. Some problems are bacterial rather than a critter, like the white raised bumps people call zoa pox. One unquarantined frag can introduce a problem that takes months to beat. The cheap insurance is a coral dip.

Dip every new coral in a commercial coral dip before it goes in the tank: swish it per the product's directions, inspect the plug, and pick off or cut away anything you don't like. Better yet, run new corals through a separate observation or quarantine tank for a few weeks so anything you missed shows itself before it reaches your display. Our guide on quarantining new and sick fish covers the QT setup, and the same thinking applies to corals.

Follow the dip product's label for dose and time exactly. Too strong or too long stresses the coral, too weak does nothing. If you're not sure which dip to grab or how hard to dip a delicate coral, ask us at the counter and we'll point you at something that matches what you're adding.

Reef chemistry is the part people get anxious about, and it's the part we can take off your plate. Every item on this list is something you can pick up from us here in Erie, and if your numbers feel off, bring a water sample in and we'll test it for you. When you're stepping up from soft corals to LPS or SPS, bring your alkalinity, calcium, and magnesium numbers and we'll help you figure out what, if anything, to dose.

We also can't promise we have every specific coral or pest med in stock on a given day. Livestock and specialty meds move fast, and we'd rather tell you straight than have you drive over for nothing. Call ahead at (814) 456-9445 and we'll tell you what's actually in the building.