Coral Compass Pro 路 $3/month 路 what's included
PAR is a snapshot of light intensity; daily light integral (DLI) is the total photons a coral gets over the day, which is what growth and color depend on. This planner converts your PAR reading and schedule, including sunrise and sunset ramps, into DLI, and works backward to the PAR you need for a target DLI so you can shorten the photoperiod without starving corals, or dim instead of raising lights.
The math
DLI (mol/m虏/day) = PAR (碌mol/m虏/s) 脳 effective hours 脳 3,600 梅 1,000,000
Effective hours = hours at full power + (ramp-up + ramp-down) 梅 2
Linear ramps deliver half their duration at full-power equivalent. Measure PAR at the coral's position with a quantum meter; fixture PAR maps are usually measured at a set depth.
Try it
Sample: 200 PAR at the coral, 8 hours at full power, 1-hour ramps each side.
Daily light integral: 6.5 mol/m虏/day (9.00 full-power-equivalent hours). PAR needed for 8 mol/m虏/day on the same schedule: 247 碌mol/m虏/s.
Sources
Pro tools include saved history and graphs for every result. Free calculators stay free: see all free reef tools.