The best reef LED lights, by the footprint they cover and what a tank costs to light

Links marked See on Amazon are affiliate links — buy through one and we earn a commission at no cost to you. How that works, and how the picks are made.

A reef light is sized by two numbers, and gallons is neither. It covers a footprint — the area under it where the PAR is still what a coral needs — at a mounting height, and it delivers a PAR at the depth the coral sits. The makers print the first as "24 × 24 in" and, with three exceptions on this page, do not print the second at all. Every figure below is the maker's own footprint (or BRS's measured one, where the maker gives none) tiled over the standard tanks by this site's engine, with a quarter of the footprint allowed past the line, because light falls off there rather than stopping; the PAR figures are only ever someone's measurement, and the table says whose. Your own tank's footprint and depth come from the tank volume calculator.

Which reef light for your tank

For each standard display: the cheapest set of any model here that covers the footprint for a mixed reef (soft coral and LPS), the cheapest from the lines with a maker and a spares network behind them, and the cheapest of those for SPS at the tighter spacing the makers and BRS give. Each cell is fixtures × price with the mount, the watts at full power, and a year at 8 hours a day.

Fixtures tiled over the footprint at the maker's or BRS's spacing, either way round, with 25 % of the footprint allowed past the glass, and only from models rated for the tank's depth (the Prime to 16 in, most pucks to 24, the Radions to 30); prices are specialist-retailer list prices on the date at the top plus the maker's mount (* = mount not priced, fixture only); a year at full power, 8 h/day, $0.18/kWh — a mixed reef runs these at a third to a half. Amazon links are affiliate links; the direct links earn us nothing.

At a glance

From each maker's page or a specialist retailer's listing, checked on the date at the top. "Covers" is the maker's footprint for a mixed reef; the SPS footprint is on each card. Prices are broad bands from specialist retailers, not Amazon, and exclude the mount.

How we ranked them

Three things, in this order. What it covers, and at what PAR — the maker's footprint where it states one, BRS's grid measurement where it took one, and a demerit for any fixture whose maker publishes no PAR figure at all, because a coverage claim without an intensity is half a spec. What it costs to cover a tank — fixtures times price plus the mount, which is the number the pick table prints and the number a listing never does. Then the ordinary things: channels and app, warranty, weight, what BRS's cost-per-PAR ranking said. Commission is not a factor; the two most expensive lines and two of the smaller makers are direct links that earn nothing.

The picks

Best overall — the reference puck

AI Hydra (32HD / 64HD)

The puck most mixed reefs from 40 to 120 gallons end up under: enough output for SPS at the top, a spread BRS measured as the most even of its size, and a mounting system everything else copies.

Type

Puck

Control

Mobius app; Apex via MXM

Draw

95–135 W

Covers, mixed

24 × 24 in · 30 × 30 in

Mount height

12 in

PAR published

By BRS only

Warranty

1 year

Street price

$480–800 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
Hydra 32HD · 95 W →	mixed 24 × 24 in · SPS 24 × 14 in · mount 12 in · tanks to 24 in deep	none published	mixed up to 30 × 12 in (6 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$580 with mount · $50/yr at full
Hydra 64HD · 135 W →	mixed 30 × 30 in · SPS 24 × 16 in · mount 12 in · tanks to 24 in deep	BRS: 335 at 12 in deep, 6 in up	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$900 with mount · $71/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker 24 × 24 in; SPS spacing is BRS's "one per 12–15 in of length"), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• BRS's grid test found the 32HD the most even 24 in spread it measured, with under 15 % of the light lost over the glass at 14 in — the number that matters more than peak PAR.
• Seven color channels and a real app; the 64HD is the 32 with double the diodes for a 30 in footprint.
• The HMS mount takes both sizes, so a tank can grow from 32s to 64s without new hardware.

What to know

• No PAR map on the maker's product page — AI publishes one on a support page that blocks fetching; the figures here are BRS's.
• The 64HD at 6 in above the water makes a 1,000 PAR hot spot in the center; BRS found 12 in the right height, and the maker says 8–10.
• One-year warranty on a $480–800 fixture, and the mount is $100 extra.

See on Amazon → Maker's page →

Best nano light — and one of three makers that print a PAR

AI Prime 16HD

A nano or a 20 to 30 gallon cube of soft coral and LPS, where one puck covers the tank and the maker actually tells you what it delivers at depth.

Type

Puck

Control

Mobius app

Draw

59 W

Covers, mixed

24 × 24 in

Mount height

8 in

PAR published

By the maker

Warranty

1 year

Street price

$280–300 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
Prime 16HD · 59 W →	mixed 24 × 24 in · SPS — · mount 8 in · tanks to 16 in deep	maker: 100 at 24 in deep, height not stated	mixed up to 30 × 12 in (6 standard sizes) · SPS —	$345 with mount · $31/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker 24 × 24 in; no SPS spacing published — the maker's own 100 PAR at 24 in is under the SPS range), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• AI prints the number the page is about: 100 PAR at 24 in — which puts LPS at the sand of a 16 in cube and soft coral anywhere in it.
• BRS's cost-per-PAR test ranked it in the six most efficient of 54 fixtures.
• Same app and channels as the Hydra at $280.

What to know

• 100 PAR at 24 in is a soft coral and LPS light; for SPS it is a top-third-of-the-tank light on a shallow cube, and the table says so.
• A "24 × 24 in" spread that BRS lists as 20 in — the spread of any puck depends on the PAR you are willing to call the edge.
• Mount is $65 extra; the freshwater version shares the name and a different ASIN.

See on Amazon → Maker's page →

The SPS standard — bought by the footprint

EcoTech Radion G6 (XR15 / XR30)

The SPS tank that is going to be photographed: the widest optics in the group (126°), the most channels, and a mounting track that spaces a row of them by the inch — at the highest price per covered square foot on the page.

Type

Puck

Control

Mobius app; Apex via MXM

Draw

95–215 W

Covers, mixed

24 × 24 in · 32 × 32 in

Mount height

9 in

PAR published

No

Warranty

1 year

Street price

$550–1,000 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
XR15 G6 · 95 W →	mixed 24 × 24 in · SPS 18 × 18 in · mount 9 in · tanks to 30 in deep	none published	mixed up to 30 × 12 in (6 standard sizes) · SPS up to 20 × 10 in (1 standard size)	$690 with mount · $50/yr at full
XR30 G6 · 215 W →	mixed 32 × 32 in · SPS 24 × 24 in · mount 9 in · tanks to 30 in deep	none published	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$1,145 with mount · $113/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker "24–30 in wide and deep"; BRS 18 × 18 in for SPS, one per 24 in for mixed), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• HEI optics at 126° give the Radion the widest, flattest spread of any puck here; BRS ranks the XR30 G6 among the six most cost-efficient in PAR per dollar despite the price.
• Eleven channels and Mobius: the most spectrum control on the page.
• The RMS track is the best way to hang three or four fixtures at exact centers.

What to know

• EcoTech publishes no PAR figure at all — a $1,000 light described as "incredibly even PAR over almost 4 ft" with no number.
• The mount is $140–145 on top. The XR30 G6 is not on Amazon at a sane price; the link is to BRS and earns nothing.
• A one-year warranty at this price is the reef forums' standing complaint.

See on Amazon → Maker's page →

Best published data — a PAR map with conditions

Red Sea ReefLED G2 115

A Reefer or any 24 in-wide mixed reef whose owner wants a number: Red Sea publishes surface and 50 cm PAR with the mounting height, so this is the one light on the page the engine can put a coral under.

Type

Puck

Control

ReefBeat app (Wi-Fi); two channels

Draw

115 W

Covers, mixed

24 × 24 in

Mount height

8.3 in

PAR published

By the maker

Warranty

2 years

Street price

$440–470 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
ReefLED G2 115 · 115 W →	mixed 24 × 24 in · SPS 24 × 16 in · mount 8.3 in · tanks to 19.7 in deep	maker: 500 at 0 in deep, 8.3 in up	mixed up to 30 × 12 in (6 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$554 with mount · $60/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker 24 × 24 in maximum spread; SPS spacing is BRS's "three over a 48 × 24 in tank"), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• Two PAR readings with conditions — 500 at the surface, 150 at 50 cm, fixture 21 cm up — which is more than every other maker here combined bar AI's one line.
• A two-year warranty, the longest of the pucks.
• BRS measured two over a 120 at 185 average PAR at 12 in and 168 at 18 in: an LPS reef, and an SPS reef with a third unit.

What to know

• Two channels: the spectrum is Red Sea's and you adjust the amount, not the color. Some people buy it for exactly that.
• The ReefLED 90 is being replaced by the G2 115; the Amazon listings are the old model bundled with an arm, so the link is to BRS and earns nothing.
• Universal arm $95 extra.

Bulk Reef Supply → Maker's page →

Best shimmer — a point source, priced by the footprint

Kessil A360X / A500X

The tank where the look matters as much as the growth: a single dense array gives the shimmer of a metal halide, and a 4.3 in puck disappears over the tank. Buy it by the footprint, and read the SPS claim with BRS's test beside it.

Type

Pendant

Control

Knobs; app needs the $109 Wi-Fi dongle or Spectral Controller

Draw

90–185 W

Covers, mixed

24 × 24 in · 36 × 36 in

Mount height

8–9 in

PAR published

No

Warranty

1 year

Street price

$450–850 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
A360X Tuna Blue · 90 W →	mixed 24 × 24 in · SPS 24 × 12 in · mount 8 in · tanks to 24 in deep	none published	mixed up to 30 × 12 in (6 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$538 with mount · $47/yr at full
A500X · 185 W →	mixed 36 × 36 in · SPS 24 × 24 in · mount 9 in · tanks to 36 in deep	none published	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$938 with mount · $97/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker: 24 × 24 in mixed reef and 20 × 20 in SPS; BRS's "two per 24 in square for SPS" is used here), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• A single-point array: the shimmer and shadow depth no multi-diode panel matches, and a 130° beam.
• The A360X is 0.8 lb and 4.3 in across — the least visible fixture here.
• Optional 55° and 35° reflectors on the A500X for deep tanks (BRS: to 36 in and 48 in).

What to know

• No PAR published by the maker for either model. BRS's A500X test put 69 % of a 24 in cube in the SPS zone at full power — not the 36 × 36 in the page claims.
• Control is knobs unless you buy the $109 dongle; the "app" is an accessory.
• The A360X is being succeeded by the A360XE (15 % more output, same draw, $499); BRS no longer prices the X.

See on Amazon → Maker's page →

Highest measured output — and the diffuser that tames it

Neptune Systems SKY

An SPS tank on an Apex, or any 30 in-wide tank that wants one fixture per 24 in of length with the highest average PAR anyone has measured over a 24 in cube — and a diffuser that makes 104 diodes look like one.

Type

Panel

Control

Apex Fusion app over Bluetooth, or AquaBus to an Apex

Draw

219 W

Covers, mixed

36 × 30 in

Mount height

9 in

PAR published

By BRS only

Warranty

1 year

Street price

$850–900 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
SKY · 219 W →	mixed 36 × 30 in · SPS 30 × 24 in · mount 9 in · tanks to 24 in deep	BRS: 390 at 12 in deep, 9 in up	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 36 × 18 in (8 standard sizes)	$1,015 with mount · $115/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker: 24 × 30 in SPS, up to 30 × 36 in for less demanding corals), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• BRS measured 390 average PAR over a 24 in cube at 100 % — the highest of the group's tested fixtures — and at 25 % it lit three-quarters of the grid in the soft coral band, so it scales down to a nano.
• A diffuser panel: no disco effect, no hot diode shadows.
• Plugs into an Apex over AquaBus; the Bluetooth app works without one.

What to know

• Neptune publishes no PAR; the figures are BRS's. 219 W from the wall is the most here per fixture.
• Mounts on the Radion pattern ($145). Not on Amazon; the link is to BRS and earns nothing.
• BRS found a 47 % drop from center to edge at 6 in deep — it wants the 9 in height, not lower.

Bulk Reef Supply → Maker's page →

Best value in a high-output puck — with a three-year warranty

Reefi Uno 2.1 Pro

A 24 to 30 in cube or a 4 ft SPS tank on two fixtures, from a small maker that publishes a bottom-of-tank PAR reading, ships the reflectors and hanging kit in the box, and warrants the light for three years.

Type

Puck

Control

Built-in Wi-Fi web app; 9 channels

Draw

270 W

Covers, mixed

30 × 30 in

Mount height

12 in

PAR published

By the maker

Warranty

3 years

Street price

$480–640 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
Uno 2.1 Pro · 270 W →	mixed 30 × 30 in · SPS 24 × 24 in · mount 12 in · tanks to 24 in deep	maker: 200–400 at 20 in deep, 11.5 in up	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$640 with mount · $142/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker: 24 × 24 in at 12 in above the water with the 90° reflector, 30 × 30 in at 15 in), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• 270 W and 114 diodes in a 7 in puck; the maker's own reading is 200–400 PAR across the bottom of a 20 in-deep cube at 11.5 in — an SPS number at the sand.
• Three-year warranty, three times the pucks from the big names.
• Two reflectors and the hanging kit come in the box; the mounting-height rule is printed (spread ÷ 2 for the 90°).

What to know

• A direct-sale brand: no BRS, no Amazon, and the link earns us nothing; support is the maker.
• The 270 W draw at full power is the highest here; run it turned down, which is what the 9 channels are for.
• The published PAR is for the earlier 180 W Uno; the 2.1 Pro should exceed it, but that is inference.

Reefi Lab → Maker's page →

Budget pick — a real reef puck for under $200

Noopsyche K7 Pro IV

A first reef, a frag tank, or a 4 ft mixed reef lit for the price of one Hydra: Osram and SemiLED diodes, six channels, a footprint the maker states — and no PAR figure, like most of the expensive ones.

Type

Puck

Control

Wi-Fi app; 6 channels

Draw

100 W

Covers, mixed

24 × 22 in

Mount height

10 in

PAR published

No

Warranty

1 year

Street price

$140–200 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
K7 Pro IV · 100 W →	mixed 24 × 22 in · SPS 20 × 22 in · mount 10 in	none published	mixed up to 30 × 12 in (6 standard sizes) · SPS up to 24 × 12 in (3 standard sizes)	$139 (mount not priced) · $53/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: maker: "around 24 × 22 in", mount 8–12 in; SPS spacing is a retailer's "two per 70–100 cm"), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• The cheapest fixture here with a stated footprint and name-brand diodes; four of them cover a 120 for less than two Radion XR15s.
• Six channels and a Wi-Fi app at $139–200.
• Light: 0.76 kg, 21 × 12.5 cm.

What to know

• No PAR published; a forum reading of 300 at the top and 100 at the sand of a 25 gal at 35 % is all there is, and it is not on this page's tables.
• Mounts are sold separately and were not priced when checked, so the cost table carries the fixture alone.
• Model names churn (Pro III at 140 W, Pro IV at 100 W, "K7 V3"); check the wattage in the listing.

See on Amazon → Maker's page →

Best PAR per dollar — the bar that fixes the ends

AI Blade Grow (30 / 39 / 48 in)

A 4 or 5 ft tank where pucks leave the ends dark, or the supplement that turns two pucks into an even spread: BRS's 54-light test found the Blade the highest average PAR per dollar of anything it measured.

Type

Bar

Control

Mobius app; pair 2 : 1 with Blade Glow

Draw

60–100 W

Covers, mixed

30 × 20 in · 39 × 20 in · 48 × 20 in

Mount height

6 in

PAR published

No

Warranty

1 year

Street price

$290–480 (2026-08)

Each size, by the box and by the physics

Size	Covers · mount · depth	Published PAR	One fixture covers	With mount · a year
Blade Grow 30 in · 60 W →	mixed 30 × 20 in · SPS 30 × 12 in · mount 6 in	none published	mixed up to 36 × 18 in (8 standard sizes) · SPS up to 30 × 12 in (6 standard sizes)	$290 (mount included) · $32/yr at full
Blade Grow 39 in · 80 W →	mixed 39 × 20 in · SPS 39 × 12 in · mount 6 in	none published	mixed up to 48 × 24 in (12 standard sizes) · SPS up to 48 × 13 in (7 standard sizes)	$390 (mount included) · $42/yr at full
Blade Grow 48 in · 100 W →	mixed 48 × 20 in · SPS 48 × 12 in · mount 6 in	none published	mixed up to 48 × 24 in (12 standard sizes) · SPS up to 48 × 13 in (7 standard sizes)	$480 (mount included) · $53/yr at full

"Covers" is the footprint for a mixed reef and for SPS (source: BRS: "12–20 in width spread" per bar; length is the bar; SPS at two bars per 24 in of width), the mounting height, and the deepest tank the maker or BRS rates it for; the size links go where the button below does. "Published PAR" is the best reading anyone has printed — the maker's first, else BRS's grid test — with its depth and mounting height. "One fixture covers" is the standard footprints a single unit lights at each spacing, with 25 % past the line allowed. Price is the specialist list with the maker's mount; the year is at full power, 8 h/day, $0.18/kWh.

Why it's here

• BRS's cost-per-PAR test: "the highest average PAR at the lowest initial cost" of 54 fixtures.
• A bar lights the whole length of the tank; a 48 in Blade over a 55 does what three pucks do for the ends.
• Tank rests included to 39 in; fanless, IP66, 100 W for the 4 ft bar.

What to know

• A 95° spread that BRS puts at 12–20 in wide — a bar is one axis of coverage, so a 24 in-wide SPS tank wants two Grows and a Glow.
• No PAR published by the maker.
• Amazon carries some sizes under changing listings; the links here are searches.

See on Amazon → Maker's page →

Gallons are the wrong unit for a light

A light does not know how deep the tank is or how much water is in it; it knows the area under it. So "rated to 75 gallons" tells you nothing a footprint would not tell you better, and it misleads whenever two tanks share a gallon count and not a shape. Take one puck — the Hydra 32HD, at its maker's 24 × 24 in for a mixed reef and BRS's one-per-12-to-15-in for SPS — and tile it over the standard sizes:

Hydra 32HD footprints (24 × 24 in mixed, 24 × 14 in SPS) tiled by this site's engine with 25 % past the line allowed; "centers" is the spacing along the tank. The same arithmetic for every model is in the pick table and on the cards.

The 29 and the 37 are the same 30 × 12 in footprint under different heights and take one puck; the 40 breeder, a "smaller" tank than the 55 by the label, takes 2 because it is 18 in wide and 36 long; the 55 takes 2 for its 48 in and would take one 48 in Blade instead. The 120 and the 125 are 48 and 72 in long, and the "bigger" 125 needs 3 pucks to the 120's 2 for a mixed reef. Buy by the footprint, then by the coral, and never by the gallons.

Who publishes a PAR — and who sells "coverage"

The other half of the spec is the intensity at depth, and it is the half the makers mostly leave out. Of the 14 models here, 3 have a maker-published PAR reading at a stated depth; 2 more have only BRS's grid measurement to go on; and 9 — including the two dearest fixtures on the page — have no published number from anyone we could find. EcoTech describes the XR30 as "incredibly even PAR over almost 4 ft," Kessil says the A500X is "36 × 36 in for SPS dominant," and neither prints a value. BRS's test put 69 % of a 24 in cube inside the SPS band under an A500X at full power; that is the closest thing to a number the claim has.

Maker figures are the product page's, with the conditions it states; BRS figures are from its 108-point in-water grid over a 24 in cube at 100 % unless the card says otherwise. "What it means" applies the coral ranges (50–150 soft, 100–200 LPS, 200–400 SPS) to the maker's readings only, interpolated between them and never beyond.

What a published PAR means for a coral

Red Sea gives two readings with the conditions — 500 PAR at the surface and 150 at 50 cm, fixture 21 cm above a 60 cm cube. Interpolated between them, a coral at 12 in sees about 240 — SPS territory at full power — and at 18 in about 166, LPS territory, with 150 at 24 in. So a ReefLED G2 over a 20 in-deep tank is an LPS-at-the-sand, SPS-at-the-top light at 100 %, and an all-LPS light at 60 %; BRS's measurement of the previous model — 235 center and 155 at the outer ring, 12 in down, two units over a 120 — sits inside that. The SKY has no maker figure, but BRS's average of 390 over the cube at 100 % means the middle of the LPS range is a 38 % setting and the soft-coral range 26 % — which is what BRS found by measurement at 25 %. The Prime's 100 at 24 in is honest and modest: soft coral anywhere, LPS in the top half of a 24 in tank, SPS only in a shallow one. For the 9 models with no reading, the card says "none published," and a rented PAR meter is the rest of the spec.

Watts, and the year

A reef light's wattage is a ceiling, not a bill: the fixtures run at the setting the coral needs, which for a mixed reef is a third to a half of full, and the maker's coverage claim is at 100 %. So the table prints two honest things — the draw at full power, and the watts per square foot of the maker's mixed-reef footprint, which is the crude efficiency figure a buyer can check without a meter — and the year at full, which is the most it can cost.

Maker's maximum draw; the footprint is the maker's or BRS's mixed-reef coverage; a year at 8 h/day and $0.18/kWh at full. Watts per square foot rewards wide optics and punishes narrow ones, which is the point — a Kessil's beam and a Radion's 126° are not the same kind of light, and neither is more efficient by this figure than the other is by a PAR meter.

How reef lights fail

• The power supply. The brick fails before the diodes on every line here; on AI and EcoTech it is a stocked part, on a direct brand it is an email. Keep it off the floor and out of the cabinet's humidity.
• Salt creep on the lens. A puck 8 in above a skimmed, splashy tank grows a film that takes 10–20 % of the PAR in a few months; the light "dims" and the owner turns it up. Wipe the lens monthly with RO water; a PAR meter shows the loss, the eye does not.
• The fan. The Hydras, Radions and Kessils are fanned and the fan is the moving part; the Blade and the SKY are not. A fan that stops throttles the fixture rather than killing it, which shows up as corals browning under a light that is "on."
• Wi-Fi and the app. Every line here except the Kessil knobs depends on an app that will be updated, and the forum threads about lights are threads about apps. The failure mode is a schedule that stops ramping, not a diode that stops lighting.
• Too much, too soon. The commonest reef-light failure is not the light; it is the corals under a new one at the old percentage. Acclimation mode exists because this happens every week.

What we'd skip

• Buying by "up to X gallons." The footprint table is the argument: a 40 breeder and a 55 share a gallon rating and not a fixture count.
• A coverage claim with no PAR behind it, at full price. 9 of the 14 models here have no published reading; the two dearest are among them. Rent a meter, or choose from the 3 that print one.
• One puck centered over a 4 ft tank. The diagram shows the ends; the coral at the ends shows them slower.
• Sizing for SPS you do not keep. The SPS column costs roughly twice the mixed column on every tank. A mixed reef with one or two acropora at the top under the puck wants the mixed count and a higher setting, not double the fixtures.
• The mount as an afterthought. $65–145 per fixture on most lines, and the cost table includes it because the listing does not.

Common questions

How high should I mount a reef LED?

Where the maker says, which for the pucks here is 8 to 12 in above the water, and higher for a wide tank than a narrow one. BRS ran 50 fixtures up from an inch above a 24 in cube and scored each height on two things: no more than a 30 % hot spot over the average, and no more than 30 % of the light lost over the glass. Low mounting gives a hot spot and shadows; high gives an even tank and lights the room. The heights on the cards are the makers', with BRS's where they measured one, and the diagram's fixture spacings assume them.

Do I need a PAR meter?

For SPS, yes, once — and you do not need to own it. Every reef club and most local stores lend an Apogee, and a $50 rental tells you more about your tank than any table on this page, because only 3 of the 14 models here have a maker-published reading to start from. Measure at the sand, the middle of the rock and the top, note the setting, and set the light by the coral's range rather than the percentage a forum thread swears by. Soft coral and LPS are forgiving enough to set by eye and by growth.

Why did my corals bleach after I upgraded the light?

Because the new fixture at the old percentage is more light — often twice as much, when a 90 W puck replaces a 30 W bar — and coral bleaches upward as readily as it starves downward. Start a new light at 30 % of its output, hold for a week, and add 10 % a week until you reach the setting the coral's PAR range calls for (the SKY, for example, reaches the middle of the LPS range at about 38 % by BRS's numbers, and the soft-coral range at 26 %). The acclimation mode in every app here does the ramp for you; the mistake is skipping it because the corals "looked fine" on day two.