Acropora
Acropora spp.
The reef-keeper's trophy coral — dazzling growth, but only in a mature, ultra-stable tank.
Difficulty: AdvancedSPS coral (advanced)
Acropora (Acropora spp.) is the coral reefkeeping builds toward — the branching, tabling and staghorn SPS behind every jaw-dropping “SPS tank.” It's also the most demanding coral in the hobby: high light, strong turbulent flow, rock-stable alkalinity/calcium/magnesium and a mature, low-nutrient tank. In the right system it grows into a showpiece; in an unstable one it can go from healthy to bare skeleton in a day. It's the endgame coral, not a starter.
Care at a glance
| Colony / form | Branching, tabling or staghorn forms (species-dependent); a healthy colony grows fast into a showpiece. |
|---|---|
| Lighting | High — roughly 200–400 PAR, with ≈250–350 the sweet spot. Colour and growth depend on strong, high-quality light, but a new frag must be acclimated up slowly to avoid bleaching. |
| Water flow | Strong and turbulent — high turnover (on the order of 20–40× the tank volume) to keep tissue clean and feed calcification. Acropora wants more flow than almost any other coral; dead spots and settled detritus are dangerous. |
| Placement | Up on exposed rockwork in strong light and turbulent flow, with room so it doesn't shade or touch neighbours as it grows. Acclimate to both light and flow before final placement. |
| Temperature | 75–82°F (24–28°C). |
| pH | 8.1–8.4. |
| Specific gravity | 1.023–1.026 (reef-standard ≈35 ppt). |
| Other targets | SPS build a dense stony skeleton and punish parameter swings far harder than LPS — keep alkalinity (≈8–11 dKH), calcium (≈400–450 ppm) and magnesium (≈1300–1400 ppm) rock-stable and test weekly. Acropora is the least forgiving of all — many acro-keepers automate dosing and prize consistency over any exact number. |
| Feeding | Largely photosynthetic in a well-lit reef; it also uses dissolved nutrients and captures tiny plankton. The real nutrient job is keeping the tank neither too dirty nor stripped bare — Acropora needs low but not zero nutrients. |
| Growth & spread | Fast once established and stable — branching and tabling colonies can become the showpiece of a tank. Easy to frag, but new frags need careful acclimation. |
| Natural range | Indo-Pacific reefs. |
The fish store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- “Acropora is just another SPS.” It's the most demanding coral in the hobby — high light, strong flow, rock-stable chemistry and a mature tank. Start with Montipora or bird's nest and work up.
- “I'll get the tank stable later.” Acropora is added last, to a system that's already proven stable for months — not something you buy to 'get into SPS'.
- “It died overnight for no reason.” RTN/STN is real and fast — a colony can strip to skeleton in hours after an alk swing or a pest outbreak. The cause is almost always a swing, a spike or a pest, not bad luck.
- “Dose more to make it grow faster.” Chasing numbers up causes the swings that kill Acropora — stability beats any single high number.
Before you buy
- A mature tank (typically 6–12+ months) with a track record of stable, tested parameters.
- Rock-stable alk/Ca/Mg — ideally automated dosing — and weekly testing.
- High light and strong turbulent flow, both acclimated for a new frag.
- A quarantine/dip routine for pests (AEFW, red bugs) — never add an un-dipped acro.
- An honest self-check: this is the endgame coral. If your parameters still swing, keep it on the wishlist.
Signs something's wrong
A struggling coral is almost always telling you about light, flow or water — here's what to watch for:
- Rapid tissue peeling off, exposing white skeleton (RTN/STN) — an emergency: frag well ahead of the receding tissue to save what you can, and find the swing, spike or pest.
- Base bleaching or browning — light not acclimated, or nutrients too high or too low.
- Polyps not extending — flow, acclimation, or an early water-quality problem.
- Tiny bite marks, pale patches or egg spirals on branch undersides — pests (AEFW); dip and inspect.
Never
- Never add Acropora to a young or unstable tank — it's the last coral in, not the first.
- Never let alkalinity swing — keep it rock-steady (automate if you can) and test weekly.
- Never add a new acro without acclimating light and flow, and without a pest dip.
- Never chase colour by pushing parameters up — stability is everything.
- Never ignore early tissue loss — RTN/STN moves in hours; act immediately.
Common acropora questions
Is Acropora hard to keep?
It's the most demanding coral in the hobby. It needs a mature, proven-stable tank (usually 6–12+ months), rock-stable alkalinity/calcium/magnesium tested weekly, high light (roughly 200–400 PAR), strong turbulent flow and low-but-not-zero nutrients. It's the endgame coral, not a beginner's SPS.
What's the difference between Acropora and Montipora?
Both are SPS, but Montipora is far more forgiving — the “gateway SPS” — while Acropora demands pristine, rock-stable conditions and a mature tank. Most reefers keep Montipora (and bird's nest) successfully well before they try Acropora.
Why did my Acropora die so fast (RTN/STN)?
Rapid or Slow Tissue Necrosis strips tissue to bare skeleton, sometimes within hours. It's almost always triggered by a parameter swing (especially alkalinity), a spike, or a pest outbreak. If you catch it early, frag well ahead of the receding tissue to save the rest, and fix the underlying stability or pest problem.
How much light and flow does Acropora need?
High light — roughly 200–400 PAR, with about 250–350 the sweet spot — and strong, turbulent flow (high turnover, on the order of 20–40× the tank volume). Acclimate new frags to both slowly to avoid bleaching.
What pests affect Acropora?
Mainly Acropora-eating flatworms (AEFW), red bugs and Acropora-eating nudibranchs. Look for bite marks, pale patches or egg spirals on branch undersides, quarantine and dip new arrivals, and never add an un-dipped acro to your display.
Sources & further reading
This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:
- Top Shelf Aquatics — Acropora Corals: The Pinnacle — PAR, flow/turnover, chemistry & stability, maturity, RTN/STN, pests, difficulty
- AllCorals — Acropora Care Guide: The Ultimate SPS Coral for Advanced Reefers — advanced framing, RTN/STN, AEFW
- Extreme Corals — Acropora Coral Care Guide — lighting, flow, placement, growth
Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your acropora is struggling, it's almost always a light, flow or water-chemistry issue — check those first and ask an experienced reefer. We never guess a care number.
🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →