Quick check
- 1Measure tank length and width to get footprint area.
- 2Check the fixture's stated coverage at reef depth, not freshwater or fish-only coverage.
- 3Match PAR to the coral goal: soft coral, mixed reef, or SPS dominant.
- 4Use multiple fixtures or bars when one light creates dark edges.
- 5Plan coral placement around measured or expected PAR zones.
Start here: I would not buy a light from center PAR alone. The edges and lower rockwork are where disappointment shows up later, especially when the plan quietly shifts from LPS to SPS.
Advice for your tank
Two checks matter more than the fixture name
Reef lighting is not just brightness. A premium fixture can still be wrong if it leaves the edges dark, and a budget fixture can be fine for a shallow soft-coral tank. ReefCrafter separates strength from spread so the recommendation follows the tank and the animals.
PAR target by reef goal
Soft corals can live in lower light. Mixed reefs need enough energy for LPS and some easier SPS near the top. SPS-dominant systems need high and even light, which is why two smaller fixtures often beat one large center-mounted fixture.
- Soft coral: ReefCrafter floor is 50 PAR at 18 inches.
- Mixed reef: ReefCrafter floor is 150 PAR at 18 inches.
- SPS dominant: ReefCrafter floor is 250 PAR at 18 inches.
- Coverage still matters even when the center PAR number looks good.
Why coverage can fail before PAR fails
A fixture might hit a strong center reading while the outer rockwork stays dim. That is why ReefCrafter has a geometric coverage floor: if the listed coverage area is under half the tank footprint, the build gets a hard blocker rather than a soft warning.
Calculate the sizing range
Adjust your tank details, then open the result in the planner.
For this goal, use the 150-250 PAR band and cover the full 864 sq in footprint.
The math and worked examples
Footprint coverage
Example: 48 in x 18 in tank = 864 square inches to cover.
A strong center beam still fails if the aquascape outside the hotspot is dim.
Coverage hard floor
Example: For an 864 sq in footprint, coverage under 432 sq in is a hard miss.
Below this line, the problem is not fine-tuning. The fixture is simply trying to light too much tank.
PAR floor by goal
Example: A mixed reef target starts around 150 PAR at 18 inches.
This keeps the coral goal attached to a number without pretending a single PAR reading describes the whole aquascape.
- Footprint area = tank length x tank width
- Coverage passes when total fixture coverage is at least the tank footprint
- Hard floor: coverage must be at least 50 percent of footprint
- PAR floor: soft coral 50+, mixed reef 150+, SPS dominant 250+ at 18 inches
Common mistakes
- Buying by tank gallons instead of footprint.
- Assuming one center light evenly covers a 4 foot tank.
- Planning SPS everywhere without checking edge and lower-rock PAR.
- Turning a light to 100 percent immediately on a new tank.
- Ignoring shadowing from rockwork and coral growth.
Before buying
- Coverage area equals or exceeds tank length x width.
- PAR target matches the coral plan at realistic depth.
- Mounting height works with your room, lid, and spill preference.
- Control app and schedule are tolerable enough that you will use them.
- Expansion path exists if you later move from LPS to SPS.
Common questions
Can soft corals grow under cheap lights?
Often yes, especially in shallow tanks, but the light still has to cover the coral zones. Cheap is less important than usable PAR, coverage, spectrum, mounting, and reliability.
Do I need a PAR meter?
You can start with manufacturer data and conservative placement, but a PAR meter rental is the best way to remove doubt once expensive corals enter the plan.
Why does ReefCrafter warn on one light for SPS?
SPS-dominant tanks usually benefit from even spread. One intense light can create a bright center and shaded edges, while two fixtures spaced apart often produce a more useful field.