Free tool

Reef Light Planner

More reef lighting money is wasted on coverage mistakes than on bad fixtures. Tell us your tank dimensions and what you want to grow, and we will tell you how many fixtures the footprint actually needs, what coverage class to shop, and where depth changes the answer.

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Step 1. Tank length (inches)

Step 2. Front-to-back width (inches)

Step 3. What you want to grow

Reference

Fixture count by tank length

LED pucks light a roughly square footprint, and PAR falls off fast outside it. The honest rule: one nano puck per 16 inches, or one full-size puck per 24 inches of tank length. This table works without any of the controls above.

Tank length	Fixtures needed	Why
Nano, up to 20 in long	One nano puck (16 by 16 in class)	A 55-watt nano fixture like the AI Prime class covers a 16 by 16 inch footprint, which matches pico and nano tanks from 5 to 25 gallons.
Standard 24 to 36 in	One full-size puck (24 by 24 in class)	Full-size fixtures in the Radion XR15 and Hydra 32HD class hold useful PAR across roughly 24 by 24 inches. A 36-inch tank works if corals stay near the center.
48 in and longer	Two or more pucks, one per 24 in	A single fixture over a 4-foot tank leaves a PAR valley at each end. Space one puck over the center of each 24-inch segment.

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The planner needs JavaScript to tailor a recommendation. The coverage table above works without it: divide your tank length by 24 and round up for full-size fixtures, or by 16 for nano pucks, then pick the fixture tier that matches your coral goals.