Reef light is sized by the light corals can actually use — PAR (photosynthetically active radiation) — not by watts or lumens. Buy too little and corals brown out and stop growing; buy too much for softies and you bleach them. The right fixture is the one that puts the correct PAR band across your whole tank at your water depth.
The ReefRig PAR Ladder
Match PAR to coral type:
- Softies (mushrooms, zoanthids, leathers): 50–150 PAR
- LPS (hammers, torches, acans): 100–200 PAR
- SPS (acropora, montipora): 200–400 PAR
Then size fixture count by coverage: fixtures = ceil(tank length ÷ fixture spread). A single point-source light covers roughly a 24-inch square of usable
growth area; a 48-inch tank therefore needs two. Tanks deeper than 24 inches lose
PAR fast toward the sand, so SPS keepers either hang fixtures higher at full power
or run a stronger light.
RULE OF THUMB
A 48-inch mixed reef needs two fixtures with ~24-inch spread each — one light leaves a dim half. For SPS in a tank over 24 inches deep, plan for 200–400 PAR at the coral, which usually means a premium fixture or a pair of mid ones.
Compare: reef LED fixtures
PAR figures are labeled by source. Only publish a PAR number you can cite: manufacturer-rated where available, community-measured (Reef2Reef) where the maker doesn't publish one, and estimated from wattage otherwise. All prices verified July 2026.
| Fixture | Watts | Coverage | PAR @24in | Price |
|---|---|---|---|---|
| NooPsyche K7 Pro IV | 100 W | 24×24 in | est. from wattage | $199.99 |
| AI Prime 16HD Reef | 59 W | 24×24 in | 100 (manufacturer) | $264.99 |
| AI Hydra 32HD | 95 W | 24×24 in | ~150 (community) | $413.99 |
| Kessil A360X Tuna Blue | 90 W | 24×24 in | ~100 (community) | ~$449 (see note) |
| Radion XR15 G6 Pro | 105 W | up to 36×36 in | not published | $529.99 |
| AI Hydra 64HD | 135 W | 30×30 in | not published | $701.99 |
| Kessil A500X Tuna Blue | 185 W | 36×36 in | not published | $849 |
| Radion XR30 G6 Pro | 215 W | ~32×32 in | not published | $999.99 |
Coverage is usable growth area, narrower than max spread. Where a maker doesn't publish a 24-inch PAR value, size by coverage and coral type — don't guess a number.
BUYER ALERT · 2026
The Kessil A360X is being replaced by the enhanced A360XE — retailers show a 'new version available' banner and new-stock A360X supply is drying up. For a new Kessil point source, buy the A360XE ($449–$499), not the outgoing A360X.
Picks by coral type and tank
- Nano softie / LPS (up to ~20 gal): AI Prime 16HD ($264.99). Its manufacturer-rated 100 PAR at 24 inches is right for softies and LPS, and it runs on the Mobius app. The NooPsyche K7 Pro IV ($199.99) is the budget alternative.
- Mixed reef, 24-inch spread: AI Hydra 32HD ($413.99), community-measured around 150 PAR at 24 inches — comfortable LPS and lower-light SPS — or a Kessil A360XE for the single-point-source shimmer look.
- SPS, standard-depth (up to 24 in): step to a Radion XR15 G6 Pro ($529.99) or Hydra 64HD ($701.99), or run two mid fixtures.
- SPS, deep or wide tank: Radion XR30 G6 Pro ($999.99), the highest-output single Radion, or a Kessil A500X ($849) over a 36-inch footprint. On a 4-foot-plus tank, plan for two.
A note on PAR data: manufacturers rarely publish a clean 24-inch PAR figure, and community measurements vary with mounting height and intensity. Treat PAR as a target band you dial in with a meter, not a spec you buy blind — which is why the table above flags exactly where each number comes from.
Bottom line
Pick the PAR band for your corals, then buy the fixture that holds that band across your whole tank — adding a second unit past 24 inches of length. For SPS in deep water, budget for a premium fixture or a pair. See the ecosystem and control-app differences in Radion vs Kessil vs AI, and have your entire system sized in the System Builder.
Wattages, coverage and prices verified July 2026 (manufacturer sites, Bulk Reef Supply, CoralVue). PAR values are manufacturer-rated, community-measured (Reef2Reef), or estimated from wattage, and are labeled as such — PAR shifts with mounting height and intensity and should be confirmed with a meter. Re-check pricing before purchase.