Most people start with the tank. How many litres, how many watts, what does a tank this size usually take? It's a reasonable place to start and it's the wrong one — because a tank is just a box of water, and the box doesn't need light. What lives in it does.

Here's how we work through it when someone calls us, in the order that actually matters — and where Natura iCon and Natura iCon MAX fit once you get to choosing hardware.

First: what are you keeping?

This single question moves the answer more than anything else about your aquarium. Soft corals and LPS evolved in gentler light and are forgiving about it. SPS — acropora, montipora, the branching corals people build display tanks around — came from shallow, bright, clear water and want considerably more.

The consequence is that two identical aquariums, same dimensions, same volume, sitting side by side, can need meaningfully different lighting purely because of what's inside them. An SPS system needs close to double what a softie tank of the same size does.

If you're keeping softies now but intend to move toward SPS, buy for where you're going. Lighting is the one part of a reef build that's genuinely painful to under-spec and then correct later.

Second: the tank's shape, not its volume

Once you know what you're keeping, the aquarium's dimensions tell you the rest — and it's length and depth that matter, not litres.

Length decides the fixture size

Light has to reach the ends of the tank, not just the middle. This is why OR4 iCon bars come in 30, 60, 90, 120 and 150 cm — you match the bar to the tank's footprint so the coverage runs the full length. Under-length your fixture and you get a bright centre with dim corners, which is the most common lighting mistake we see.

Depth decides the intensity

Light weakens quickly as it travels through water, so a tall tank needs more output than a shallow one holding exactly the same volume. A 60 cm-deep aquarium is a genuinely different lighting problem from a 40 cm-deep one, even when the number on the box is the same. This is the main reason volume alone is a poor guide.

Third: choosing your fixture

Two ways to light a reef. A single fixture above the tank, or an array of bars along it. Both work — but they solve the problem differently, and for most aquariums one of them is clearly the easier life.

Natura iCon — the single-fixture answer

A complete reef spectrum in one unit. Natura iCon carries 78 mixed dual-chip 6 W LEDs — 156 chips in total across 13 LED types — covering the full 390–740 nm biological spectrum on six independent channels. One fixture covers an 80 × 60 × 60 cm reef tank.

The point of a fixture like this is that you aren't assembling a spectrum from separate bars. The daylight, the blues, the violets and the actinic are already in there, on channels you tune from the app rather than by buying another bar. One unit, one power supply, one thing to mount.

Across the 50 aquariums we've specified, Natura iCon is a valid answer for 34 of them — tanks from 45 cm to well over a meter.

Natura iCon MAX — for larger, deeper and SPS-dominant tanks

MAX is not a trim level. It's twice the light engine: 156 dual-chip 6 W LEDs, 312 chips, drawing 280–290 W against the Natura iCon's 145–150 W. One unit covers 120 × 60 × 60 cm — half a metre more length at the same depth.

What makes it interesting isn't only the output. MAX carries the widest blue spectrum we've built, with four distinct bands in a single fixture — Ice Blue at 470–480 nm, Blue at 450–470 nm, Violet at 420–430 nm and UV/Violet at 390–415 nm. That's the blue and actinic content of several separate bars, already inside one unit. For an SPS-dominant tank, it's the shortest route to the colour people build these systems for.

It also carries Sun & Moon Sync with automatic geolocation, and Sync Calendar — seasonal spawning control, which came out of our work with aquariums running coral spawning programmes.

A useful rule of thumb: if your tank is up to about 80 cm long, Natura iCon is likely your fixture. Beyond that, or if the tank is deep, or if you're running SPS and chasing colour, MAX is the one — and on aquariums past 150 cm, two of them. In 26 of our 50 specified tanks both are listed as valid, so there's a real choice to make in the middle of the range rather than a hard cutoff.

OR4 iCon bars — when you want to build it yourself

Bars run along the length of the tank and let you compose the spectrum yourself, bar by bar, in 30 to 150 cm lengths. You can start with two and add more as the tank matures, and the Osix controller runs several as a single fixture. It's the flexible route — more decisions to make, more mounting to solve, and more scope to tune the tank exactly to your taste.

What no chart can tell you

Three things shift the answer that no table can account for. Aquascape — a tall rock structure shades everything behind it. Placement — the same tank is several different light environments between the sand bed and the top rock, which is why corals get moved. And your own eye — two reefers with identically specified tanks will often run them differently, and both will be right.

Treat any recommendation, ours included, as a well-informed starting point. Then watch your corals, because they'll tell you more than a specification will.