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Reefscape
SPS vs LPS lighting
Both SPS (small-polyp stony) and LPS (large-polyp stony) feed on light through their symbionts, but they sit at different reef depths, grow different polyp sizes, and tolerate sudden change differently—so the useful light bands in a tank diverge. Fixture wattage and LED count do not help much; what matters is the PAR that actually reaches the coral’s height. Softie starters are in starting with soft corals; shelf height and rock platforms pair with live-rock layouts that leave swim lanes.
Where do they differ?
SPS such as Acropora and Montipora sit nearer the reef crest: small polyps, fast growth, heavier reliance on steady bright light and steady alkalinity. A sudden jump up or down in light hits color and growth first.
LPS such as hammer, torch, and frogspawn sit mid-reef to a bit deeper: larger polyps, and many still catch meaty food, so they lean a little less on photosynthesis alone. Moderate light is often enough; too much shows up as daytime retraction and pale upper surfaces.
A mixed reef is rarely one flat brightness. Think in bands: upper rock for SPS, mid-to-lower shelves for LPS, sand-line shade for mushroom corals and some soft corals. A weak fixture will not carry SPS just because you want them; a strong fixture with LPS under the hot center will burn them first.
Rough PAR bands
PAR (photosynthetically active radiation) is µmol/m²/s at a point. These are common home-reef starting bands—species vary; trust a meter in your tank and the coral’s response:
| Type | Common PAR band | Usual placement |
|---|---|---|
| Most LPS (hammer, frogspawn, torch, bubbles, and kin) | About 75–200 | Mid to lower shelves; off the hot spot under the fixture |
| Hardier SPS (some Montipora, bird’s nest, stylophora) | About 150–250 | Upper-mid; a steadier on-ramp |
| Acropora and other demanding SPS | About 200–350+ after acclimation | Upper rock; start lower, then move up |
| Soft corals / mushroom corals (for contrast) | About 50–150 | Mid-low; see the softie starter guide |
Without a PAR meter, height is a rough split: the top 10–15 cm under the light is often the strong band, mid-water the middle band, and near the sand the weak band. New pieces belong in a weaker spot first—safer than gluing them under the lamp on day one.
How to split placement
- SPS high: Acropora and demanding Montipora on upper shelves, close to the light but not drying at the surface. Leave gaps between branches so they do not shade or scrape each other.
- LPS mid-low: hammers, torches, and frogspawn on mid shelves or sand-edge pads. Same-genus sweepers need about 10–15 cm of reach—do not jam them into SPS branches.
- Mixed reefs need not run flat-out: if LPS are the main show, light them so one or two hardy SPS can sit up top; maxing the fixture for three Acropora often cooks the LPS below first.
- Flow follows light: brighter light means faster metabolism and more mucus and detritus to clear. Upper SPS want steady, irregular through-flow; LPS want indirect flow—do not aim a wavemaker straight into the tentacles.
How to acclimate to light
Shop and shipping light is often dimmer than a display, and you rarely know the exact number. Sudden change hurts more than missing a target PAR by a little. Two common approaches:
- Low then high (placement): park a new piece on the sand or in lower shade for days to a week, then step it up every few days. Stop if polyps retract or tissue pales.
- Dim then bright (fixture): if it already sits in its final spot, start the relevant channels around 40–50% of your normal setting, then add about 10% every few days over two to four weeks. Built-in acclimation modes help when the fixture has them.
Symbionts adapt on a weeks scale. Moving from shade to the hot center in one day—or slamming intensity from half to full—is a common bleaching trigger.
Photoperiod
About 8–10 hours of main spectrum covers most tanks; add 30–60 minutes of ramp up and ramp down. A short blue viewing window at each end is fine—stretching the total day to sixteen hours mostly feeds algae.
Once intensity and length are set, keep them the same day to day. Corals tolerate a modest target better than a bright–dim–brighter yo-yo.
Things to watch
| What you see | Likely why | What to try |
|---|---|---|
| Pale upper surface, daytime retraction | Too much light, or too fast a jump | Move down one shelf, or lower intensity; climb again only when stable |
| Brown, slow growth | Chronically low light (especially SPS) | Nudge up or raise intensity a little; confirm alkalinity is steady |
| LPS closed only at peak light | Sitting in a hot spot | Shift to a mid side shelf, off center |
| SPS tips white, base still colored | Local overexposure, or flow not clearing waste | Ease light or improve indirect flow; do not only dose nutrients |
| Whole tank retracts after a fixture swap | Spectrum or intensity jumped too hard | Ramp with an acclimation mode; move pieces lower if needed |
Three habits hurt more directly:
- Choosing coral by wattage: watts are not PAR; coverage and optics differ a lot at the same power.
- New SPS glued under the lamp: low-light shop stock often bleaches in week one.
- Maxing the fixture for SPS while LPS sits in the hot center: mixed reefs need zones, not one brightness for everything.
Checking it in the studio
Magic Reefscape renders a full-tank composition: rock height, coral groups, and a sense of light. If the render packs frags only on the crest with no mid shelves, real PAR bands for SPS and LPS will be hard to split too.
Check the picture for high spots left for Acropora-type pieces; hammers and torches on mid side shelves rather than under the hot center; and weak-light room near the sand. Whether alkalinity is steady or the fixture is still ramping is not in the image—follow this page for that.
Softie light bands are in starting with soft corals; individual species live in the Feedbook.
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2026-10-16