Quick answer: Plan a DIY LED reef light around the corals you intend to keep, with adjustable colour channels, intensity control and a fixture layout you can measure in the tank. Choose the spectrum and output before buying LEDs; use the build checklist below to plan the housing, cooling, driver and power supply.
This guide separates coral-lighting evidence from electrical planning. It covers what the available research supports, a conceptual assembly sequence and a running-cost example. It does not provide a universal PAR target or a mains wiring diagram.
How much light do reef corals need?
Start with the coral group rather than a wattage-per-tank rule. Many aquarium corals host zooxanthellae, symbiotic algae that photosynthesise and supply sugars to their host, as described in Wikipedia's reef aquarium overview.
NOAA reports that as much as 90% of the organic material produced by these algae through photosynthesis transfers to coral tissue. This describes a biological relationship, not a fixture efficiency rating or an LED output target. NOAA's coral and algae explanation
The following relative categories come from Wikipedia's reef aquarium overview; use them to frame the design, not as numerical setpoints.
| Coral group | Relative light requirement according to Wikipedia | Design decision |
|---|---|---|
| Mushroom and polyp corals | Very little light | Include a usable low-output setting |
| Large-polyp stony corals, including brain, bubble and torch corals | Moderate light | Plan adjustable output instead of a fixed maximum |
| Small-polyp stony corals, including Acropora and Montipora | High-intensity light | Make measured intensity part of fixture selection |
For a mixed tank, decide which animals the fixture must serve before choosing the LED count. The table cannot tell you the required electrical wattage: it supplies relative biological needs, not a conversion between coral type and watts.
What should you measure: PAR, watts or colour temperature?
Use photon measurements to describe the light field and watts to calculate electrical consumption. According to Wikipedia's PAR definition, photosynthetically active radiation covers 400–700 nm; photon flux density, or PPFD, is expressed in µmol/m²/s, meaning micromoles of photons per square metre per second.
Keep the quantities separate when comparing candidate fixtures:
- Watts: electrical power; useful for the power budget and electricity bill.
- Colour temperature: a colour descriptor expressed in kelvins.
- PPFD: the photon measurement used here to describe intensity at a location, following Wikipedia's PAR definition.
Plan measurement locations where the corals will sit, including the centre and edges of the intended coverage. Compare channel settings at the same locations so the comparison has a defined basis. Do not turn an electrical-power calculation into a claimed coral-lighting result: the equations below calculate consumption only.
Is blue light the right choice?
Blue and purple channels have species-specific experimental support, but the study does not establish a recipe for every reef. According to a controlled 8-week study of Goniopora columna, blue light at 440–470 nm and purple light at 400–430 nm promoted growth and survival; the authors concluded that 400–470 nm could be the main illumination range for this species. Goniopora lighting study
According to the same study, white light had a higher measured PAR value than blue or purple but caused polyp contraction, leading the authors to favour blue and purple for this species. That comparison argues against choosing a channel solely because its PAR reading is higher. Study measurements and observations
For a DIY design, make channel adjustment part of the brief. Decide which spectrum you are trying to evaluate, then select components for that design. This evidence does not specify a blue-to-white LED ratio, a red-channel requirement or a UV component; none is prescribed here.
How to plan and assemble the fixture
Build from a defined electrical load and an adjustable lighting layout. For a simple assumed low-voltage load of 60 W at 24 V, the current calculation is P = V × I, so I = P ÷ V = 60 ÷ 24 = 2.5 A. This is load arithmetic, not a power-supply rating recommendation or a complete driver design.
Use this sequence to turn the plan into a parts list and assembly checklist:
- Define the layout. Match the housing outline to the area you intend to illuminate. Allocate space for LED modules, their mounting surfaces, heat sinks, cable access and any fans included in the design.
- Choose the channels. List the LEDs or modules for each colour and the intended adjustment controls. Treat viewing appearance and the coral-lighting evidence as separate selection criteria.
- Match the electrical components. Check the selected LEDs, drivers, controller and supply together for voltage, current and control compatibility. Calculate each intended load before selecting its supply; include fan loads if applicable.
- Assemble the mechanical parts. Fit the housing, LED mounting surfaces and cooling components according to their component instructions. Plan access for replacing a fan or module without dismantling the whole fixture.
- Review the installation. Resolve mounting security, splash exposure, cable routing and the location of power equipment before placing the fixture over water. Have a qualified electrician handle mains-voltage wiring.
- Commission the controls and coverage. Confirm that each channel responds as intended, then measure the proposed settings at the planned coral locations. Choose settings using evidence relevant to the animals being kept.
The useful elements of a DIY parts list are the housing, LEDs, heat sinks, drivers, supply and controls. A shopping list alone cannot establish their compatibility. The assumed current calculation above gives a load figure; it does not specify LED counts, wiring topology or supply headroom.
Calculate the running cost before choosing a schedule
Use total electrical input and operating time to estimate the bill. The electricity cost calculator is the closest tool here for budgeting a complete reef fixture; the LED calculator hub provides the site's other electrical planning tools.
Worked example — all inputs assumed: a complete fixture drawing 60 W, quantity 1, running 8 hours/day, for 30 days/month, at $0.20/kWh. These are budget assumptions, not a recommended coral photoperiod or a quoted electricity tariff.
Following the calculator's formulas:
- Total power = wattage × quantity = 60 × 1 = 60 W.
- Daily energy = total watts × hours ÷ 1,000 = 60 × 8 ÷ 1,000 = 480 ÷ 1,000 = 0.48 kWh/day.
- Monthly energy = daily energy × days = 0.48 × 30 = 14.4 kWh/month.
- Daily cost = daily energy × rate = 0.48 × $0.20 = $0.096/day.
- Monthly cost = monthly energy × rate = 14.4 × $0.20 = $2.88/month.
Choose the biological schedule separately. According to the Goniopora study, blue-light groups exposed for 6 versus 12 hours/day showed no significant difference in polyp count. That result concerns the studied species and conditions; it does not establish a general reef-tank timer setting. Study photoperiod comparison
FAQ
Can I choose a reef light by watts alone?
Use watts for electrical budgeting and photon measurements for the light assessment. According to Wikipedia's reef aquarium overview, light requirements differ between mushroom, large-polyp stony and small-polyp stony corals, so coral selection must inform the design.
Is the bluest-looking setting automatically best?
No universal colour setting follows from the evidence here. According to the Goniopora lighting study, blue and purple illumination suited that species under the experimental conditions; this does not validate every blue-looking fixture.
Can too much light hurt corals?
Yes. According to Wikipedia's coral bleaching overview, high light can contribute to breakdown of the coral–zooxanthellae relationship, alongside stressors such as abnormal temperatures and some diseases.
Do I need a separate power supply for every colour?
Do not make colour count the deciding rule. Plan the supply arrangement around the selected driver and control requirements, and calculate the load using P = V × I before deciding how to power the channels.
What PAR target should I use?
The evidence cited here does not establish numerical targets for each coral group. According to Wikipedia's reef aquarium overview, those groups have different relative needs; use species-specific guidance to set a target rather than inventing one from fixture wattage.
Jack Shi
Founder & editor, LEDaskJack Shi builds and writes LEDask, an independent LED-lighting tools project operated by clooms. He designs the calculators, checks their formulas and reference values against published engineering data, and writes the guides across the site.
