Acan Coral Care Guide

The Basics

Acan Care at a Glance

• Keep Acans in low to moderate light. Roughly 50–150 PAR is a good starting range.
• Give them gentle to moderate, indirect flow. You want enough movement to keep debris from settling without constantly folding or pinning down the fleshy polyps.
• Leave room around neighboring corals. Acans can expand well beyond their skeleton and can sting what they touch.
• Prioritize stable water parameters. Keep salinity and alkalinity steady, avoid sudden swings, and don't drive nitrate or phosphate to zero.

Care Guide

Acans generally prefer low to moderate light, with roughly 50–150 PAR being a practical starting range. Corals sold as Acans don't all respond the same way, so if you don't know the coral's previous lighting, start on the dimmer side (50–80 PAR) and give it time to adjust before moving it into brighter locations. Watch for normal inflation, good color, and consistent extension before gradually increasing the light. Acans usually handle too little light better than a sudden jump into intense lighting.

Care Guide

Acans prefer gentle to moderate, indirect flow. Aim a pump past the coral or bounce the current off glass or rock rather than pointing a pump directly at the colony. Random or changing movement is better than water pushing from the same direction all day. Tank wide flow numbers and pump settings don't tell you exactly what reaches the coral, so watch the tissue instead. Adjust the pump or move the coral until its fleshy polyps sway gently without being flattened, folded over, or constantly pushed to one side.

Choose the Acan's location based on the light and flow it actually receives, not tank height and equipment settings. Lower rockwork or a slightly raised, clean spot on the sand bed often works well, as long as detritus can't collect around the coral and it's not directly under the most intense part of your light. Give the coral enough open space to expand and extend feeding or sweeper tentacles at night.

Care Guide

Acan Water Parameters

These are practical targets for your tank. A steady reading you can trust often beats chasing a perfect number.

High confidenceModerate confidenceLimited evidence or sources reviewedReflects how consistently the reviewed sources agree on each range.

Care Guide

Wait until you see feeder tentacles out, often after the lights dim, then set a small piece of food on the responsive polyps with a pipette. Cut the local flow briefly if you need to and turn it back on once the food is captured. If a polyp doesn't respond, take the food back out instead of adding more. You don't have to feed at night forever — Acans adapt to a daytime routine if you feed at a consistent time.

Frequency

Optional, 1–3 times weekly

Growth

slow to moderate

Acans grow at a slow to moderate pace. Look for tissue creeping over the cut skeleton and new polyps budding along the colony's edges. How fast that happens depends on the species, light, feeding, and chemistry, so compare dated photos instead of expecting a set number of new polyps each month. Meta Reef's free tank tracker keeps a photo history for each coral, which makes those comparisons easy.

Large or frequent portions tend to sit on the tissue, draw in fish and invertebrates that tear at the polyps, and raise your nutrients.

Care Guide

Acanthastrea can damage nearby corals two ways: nighttime sweeper tentacles and direct digestive-tissue contact. Acanthastrea echinata sits at the aggressive end of the corals sold as Acans, and even a small frag can defend more space than you'd expect once it settles in. Reach varies colony to colony and follows your flow — sweepers tend to find whatever sits downstream.

Begin with 4–6 inches. Treat that as your starting point, and check the coral with a dim flashlight in the evening after your lights have been off for a few hours. If it's reaching farther than that, give it more room.

Don't assume two corals are safe to touch just because both were sold as Acans. Unrelated colonies, Micromussa, Homophyllia, and other fleshy LPS can all damage one another on contact — and when an echinata reaches a Micromussa lord, expect the lord to take the damage.

Care Guide

Acclimating a New Acan

When you know how the coral was kept before, match those conditions as closely as you can. After that, change only one major variable at a time, so if it gets stressed you know why.

1. 1

   Float the sealed bag in your tank or sump for 15–30 minutes to match temperature, then gradually mix in tank water — and keep the shipping water out of your system.

2. 2

   Inspect the frag under white light before it goes anywhere near your rocks. Healthy tissue looks inflated and fleshy with no exposed or receding skeleton at the edges. Handle it by the plug or skeleton, not the tissue, and keep it underwater as much as possible.

3. 3

   Dip it in a coral dip following the label directions, then rinse it in clean saltwater before it enters the tank. Dips knock down flatworms and other hitchhikers but don't catch everything, so a 2–3 week quarantine is better if you have a tank set up for that.

4. 4

   Place it low in the tank — not directly under the brightest part of your light — in gentle, indirect flow, and secure the frag so it can't fall. Around 50–80 PAR is a good starting spot, clear of neighboring sweepers.

5. 5

   Give it a week or two to adjust before moving it. Look for daytime inflation, a feeding response after dark, and healthy tissue at the margins before raising the light. Some sulking after a move is normal for a fleshy LPS.

Health

Troubleshooting Acan Corals

ID & Buying

Acan Identification

When identifying a coral labeled "Acan," the first thing to know is that the name can refer to several different corals. Years ago, both Acan Lords and bowerbanki were classified in the Acanthastrea genus. Taxonomy has changed since then and Acan Lords are now Micromussa lordhowensis, while bowerbanki is now Homophyllia bowerbanki. The old names stuck around in the hobby, but once you know what to look for, these corals get easier to tell apart.

Micromussa lordhowensis, still commonly sold as an Acan Lord, usually looks like a cluster of plump, round polyps. Each mouth and fleshy rim is fairly easy to pick out. Homophyllia bowerbanki tends to have larger, less uniform corallites that can look stretched or irregular rather than neatly round. Blastomussa can look surprisingly similar when fully inflated, but its polyps grow from more distinct skeletal cups or branches instead of forming the same tightly packed colony.

Acanthastrea species, particularly Acanthastrea echinata, have a different look. It typically grows across the rock as an encrusting colony or low mound, with tightly packed corallites, thick walls, and a rougher honeycomb appearance. When the tissue retracts, you may see concentric folds around the mouths and the prominent skeletal teeth characteristic of echinata.

If you're still unsure, don't put too much weight on the seller's label or the coral's color. Look at its growth pattern and, whenever possible, the skeleton beneath the flesh. A white light photo while the coral is open and another when it's partially retracted can make the differences much easier to see.

What to look for

• Acanthastrea echinata grows as a crust or low mound, its round, thick-walled corallites packed so tightly they share walls
• Long, pointed teeth on the skeleton — easiest to spot where the tissue has pulled back on its own, no need to touch the coral
• Thick, fleshy tissue that folds into rings over each corallite when the polyps close

ID & Buying

What to Look For When Buying Acan Corals