Acropora Care Guide: Lighting, Flow, Feeding and Placement
Acropora is widely considered the "final boss" of coral keeping — not because the coral itself is fussy to feed, but because it demands a tank that is already dialed in before it ever goes in the water. This guide breaks down the actual numbers for lighting, flow, chemistry, and placement, and treats ongoing water maintenance as the real day-to-day job of keeping Acropora alive and colorful.
Is Your Tank Ready for Acropora?
Acropora is not a first coral, and it usually isn't a first SPS coral either. Before adding one, most successful keepers have already run a mature, stable tank for six months or longer with proven, tested parameter control — not just a tank that "looks fine."
A basic readiness checklist:
- Calcium, alkalinity, magnesium, nitrate, and phosphate have been tested and stable for several weeks to months, not just checked once.
- Lighting and flow equipment capable of high-PAR, multidirectional output is already installed and running.
- You have successfully kept easier corals (soft corals or LPS) for a meaningful stretch without losses.
- You have a plan for testing frequency and dosing before the coral arrives, not after problems start.
LPS vs. SPS: Why Acropora Is a Step Up
LPS (large-polyp stony) corals are fleshy, forgiving of parameter drift, and tolerate moderate light and flow — good training wheels for reef keeping. SPS (small-polyp stony) corals, the group Acropora belongs to, have thin tissue over a dense skeleton, demand high and stable light and flow, and punish chemistry swings quickly. If you're still fighting algae or chasing parameters with your LPS, it's worth solving that first.
Lighting: PAR, Spectrum, and Acclimation
Target roughly 300–450 PAR at the coral's position, with some hardy, deeper-water-adapted varieties tolerating 500+ PAR once fully acclimated. Sources disagree on an exact number because PAR needs vary by species and by the depth the parent colony was collected or grown at — treat the range as a starting point, not a target to chase precisely.
- Use full-spectrum LED fixtures or T5HO tubes; either can hit the required intensity.
- New frags should be acclimated gradually over 2–4 weeks — start at lower intensity and shorter photoperiod, then ramp up gradually.
- A PAR meter is the only reliable way to confirm what your coral is actually receiving; eyeballing brightness is not a substitute.
Photoperiod
An 8–10 hour main photoperiod is typical. Some keepers cap peak-intensity hours to around 7, using ramp-up and ramp-down periods with enhanced blue spectrum at "sunrise" and "sunset" to support coloration without adding unnecessary high-intensity hours.
Flow: Chaotic, Not Laminar
Acropora wants strong, random, multidirectional flow — the kind that moves polyp tissue without blasting it flat or tearing it. Straight, laminar flow from a single point source isn't enough; use multiple powerheads or wavemakers running alternating or randomized patterns instead.
A common rule of thumb is 50–150x total tank volume in turnover per hour, but this is a starting point, not gospel — actual need varies with tank shape and stocking density. The better indicator is the coral itself: polyps should sway and extend, not stay clamped shut or thrash violently.
| Tank volume | Rough turnover target (50–150x/hr) | Signs flow is right |
|---|---|---|
| 20 gal (76 L) | 1,000–3,000 GPH | Tissue ripples, polyps extended |
| 40 gal (151 L) | 2,000–6,000 GPH | Detritus stays suspended, not settling |
| 75 gal (284 L) | 3,750–11,250 GPH | No dead spots behind rockwork |
| 120 gal (454 L) | 6,000–18,000 GPH | Multiple pumps needed, randomized |
Placement: Space, Light, and Aggression
Acropora is chemically and physically aggressive. Give colonies several inches to a foot or more of clearance as they grow, because contact between Acropora colonies — via sweeper tentacles or allelopathic chemical release — causes rapid tissue damage at the point of contact, sometimes to both corals.
- Place light-loving branching types mid-to-upper tank where PAR is highest.
- As colonies grow, monitor and reposition to prevent shading neighbors or blocking flow to itself and nearby corals.
- Layer your rockwork so SPS occupies separate structures from LPS and soft corals where possible — this reduces chemical warfare across coral types, not just Acropora-to-Acropora spacing.
Other SPS Worth Knowing
Acropora sits within the broader small-polyp-stony group alongside Montipora, Stylophora, and Seriatopora. All share the high-light, high-flow, stable-chemistry profile, but growth form and hardiness vary — Montipora, for example, is generally considered more forgiving than most Acropora. You can browse the full range of SPS corals or compare against more forgiving LPS hard corals if you're still building experience.
Water Parameters: The Real Workload
Stability matters more than hitting an exact number. Frequent overcorrection does more damage than a steady, slightly-off baseline.
| Parameter | Target range |
|---|---|
| Calcium | 420–450 ppm |
| Alkalinity | 7.5–9 dKH |
| Magnesium | 1,300–1,400 ppm |
| pH | 8.1–8.4 |
| Temperature | 76–80°F (24–27°C) |
| Salinity | 1.025–1.026 SG |
| Nitrate | ~2–10 ppm (up to 20–40 ppm tolerated by some) |
| Phosphate | ~0.01–0.05 ppm |
The Nitrate Debate
Sources disagree here. Some recommend near-zero nitrate; others point to a specific N:P ratio of roughly 50:1–100:1, arguing that low-but-present nitrate actually supports better coloration and stability than ultra-low nutrients. Ultra-low is not automatically better. For most keepers, moderate, stable, low nutrients with a balanced ratio is the safer target than chasing zero.
pH and Gas Exchange
Keep pH within 8.1–8.4. Nighttime CO2 buildup (from respiration, with photosynthesis paused) can cause a temporary dip. Good gas exchange and skimming, plus stable alkalinity, help smooth this out rather than letting pH swing daily.
Essential Reef Supplements: The "Big Three"
Calcium, alkalinity, and magnesium are consumed continuously as SPS builds skeleton, and all three must be replenished — a growing Acropora colony will draw them down faster than an established LPS-only tank.
Three common replenishment methods, and when each fits:
- Two-part liquid dosing (calcium + alkalinity): simplest to start with, well suited to smaller or lightly-stocked tanks.
- Kalkwasser (limewater) via auto top-off: replenishes calcium and alkalinity as evaporated water is replaced; scales with your top-off rate.
- Calcium reactors (CO2 plus calcium media): the low-labor, high-capacity option once SPS biomass and demand outpace manual dosing, common on larger or heavily-stocked SPS systems. They require monitoring effluent pH/alkalinity and periodic media refills.
Test before dosing — dosing without testing is guessing. Test every 2–3 days while establishing a routine, then move to weekly or biweekly once parameters hold steady.
If Alkalinity Overshoots
Don't correct suddenly. Dilute with fresh saltwater or scale back dosing gradually — a sudden swing in the other direction can shock corals just as badly as the original overshoot.
Feeding Acropora
Acropora gets most of its energy from photosynthesis via zooxanthellae, so feeding is supplemental, not essential for survival. That said, targeted feeding a few times a week can boost growth and coloration:
- Amino acid supplements
- Phytoplankton
- Small zooplankton — rotifers, cyclops, or coral-specific powders and pastes
Feed sparingly. Overfeeding risks nitrate and phosphate spikes that fuel nuisance algae, which in turn shades or irritates corals — undoing the benefit of feeding in the first place.
Acclimation, Dipping, and Fragging
Dip and quarantine every new frag or colony — using iodine or a commercial coral dip — before it enters the display, regardless of source. This is the main defense against introducing pests like Acropora-eating flatworms or red bugs, which can devastate a colony before you notice anything wrong.
Fragging (cutting and mounting healthy branch tips) is a normal propagation practice, and it doubles as a rescue strategy: if part of a colony is dying, cutting healthy tissue away from the affected area and mounting it separately can save the rest.
Growth and Coloration
Color intensity comes down to light spectrum/intensity and stable, low-nutrient water — not genetics alone. Wild-collected Acropora is typically drab compared to the vividly colored, selectively-bred frags widely available today, which is part of why captive-bred stock is favored by most reef keepers.
A Note on Price
Rare, highly-colored Acropora morphs can command high frag prices. This reflects slow growth rates, limited supply, and unique coloration patterns rather than any special care requirement — it's simply collector culture within the hobby.
A Rough Acclimation Timeline for New Frags
| Week | Light | Flow | Placement |
|---|---|---|---|
| 1 | Low intensity, shorter photoperiod | Gentle, indirect | Lower/mid tank, shaded area |
| 2 | Increase intensity moderately | Increase slightly | Same position, observe polyp extension |
| 3 | Approach target PAR | Near target flow | Move toward intended final spot |
| 4 | Full target PAR/photoperiod | Full target flow | Final placement, monitor closely |
Watch the coral, not just the calendar — if polyps retract or tissue pales at any step, hold that stage longer before increasing intensity.
Supporting Equipment
A few pieces of gear do most of the heavy lifting in keeping the above parameters stable:
- Protein skimmer: exports dissolved organics before they break down into nitrate and phosphate, reducing algae and stabilizing chemistry.
- Sump: adds water volume (which buffers swings) and houses equipment out of view.
- GAC/GFO reactors or filter socks: control odor, tannins, and excess phosphate; replace media roughly every 4–6 weeks.
- Auto top-off (ATO): keeps salinity constant as water evaporates, especially important paired with a heater/controller.
- Reef-grade salt mix: consistent trace elements underpin long-term parameter stability far more than any single dosing tweak.
- Controllers and auto-dosers: reduce manual labor and human error in maintaining the big three as coral biomass grows.
- Chiller: worth considering if lighting or room heat pushes temperature above roughly 80°F (27°C), particularly in summer — heat stress and swings are hard on SPS.
Full-spectrum fixtures suited to SPS-level PAR can be browsed under lighting if you're upgrading equipment before your first Acropora purchase.
Common Mistakes and Troubleshooting
- Adding Acropora too soon, before parameters are tested and stable — a leading cause of early bleaching or rapid tissue necrosis (RTN).
- Sudden parameter swings — large water changes or dosing jumps — triggering RTN or slow tissue necrosis (STN).
- Skipping the light acclimation ramp, causing bleaching or tissue burn under full-intensity lighting.
- Skipping dip/quarantine, introducing Acropora-eating flatworms or red bugs undetected.
- Overfeeding zooplankton foods, spiking nutrients and fueling algae.
- Placing colonies too close together, triggering allelopathic and physical tissue damage at contact points.
- Chasing perfect numbers instead of stability — frequent overcorrection is often worse than a steady, slightly-off baseline.
- Ignoring flow changes as colonies grow and start blocking circulation to themselves or neighbors.
A Simple Visual Checklist
Before assuming the worst, check:
- Polyp extension — retracted polyps for more than a day or two signals stress.
- Color shift toward brown — usually points to low light/spectrum mismatch or elevated nutrients.
- Tissue recession pattern — a spreading white band suggests RTN/STN in progress; localized paling is more often light or flow related.
Frequently Asked Questions
Is Acropora good for beginners?
Generally no. Most successful keepers recommend building experience with soft corals and LPS first, and running a stable, tested tank for months before attempting Acropora or other SPS.
What PAR do I need for Acropora?
Roughly 300–450 PAR at the colony, introduced through gradual acclimation. Some hardier species tolerate higher intensities once fully adjusted.
How much flow does Acropora need?
Strong, random, multidirectional flow — a rough starting point is 50–150x tank volume turnover per hour, adjusted based on how the coral's polyps and tissue respond rather than chasing an exact GPH figure.
Do I need to feed Acropora?
Not strictly — most of its energy comes from light via zooxanthellae — but occasional target feeding of amino acids and small zooplankton can support faster growth and better color.
Why is my Acropora losing color or turning brown?
Usually a light/spectrum mismatch, elevated nutrients, or a general stress response. Check your PAR reading and test nitrate/phosphate before making changes.
What causes RTN/STN in Acropora, and can it be stopped?
Sudden parameter shifts, pests, shipping stress, or physical damage are the usual triggers. Cutting away healthy fragments from the unaffected part of the colony and fragging them separately can save part of it even if the rest is lost.
Do I need a calcium reactor to keep Acropora?
No. Small or lightly-stocked tanks can maintain parameters fine with two-part dosing or kalkwasser. Reactors become worthwhile once SPS biomass and calcium/alkalinity demand outpace what manual dosing can keep up with.
How do I know if my tank is ready for Acropora?
Look for stable, tested calcium, alkalinity, magnesium, nitrate, and phosphate over several weeks to months, lighting and flow equipment already capable of SPS-level output, and a track record of successfully keeping easier corals.
Once your parameters, lighting, and flow are dialed in, browse FishyHub's selection of corals to compare Acropora against other SPS and LPS options before adding your next colony.
