Aquarium Lighting Calculator
Estimate PAR at substrate from your fixture wattage, type, and tank depth — then map to the right plant level (very-low, low, medium, high, CO2-required). The PAR spectrum bar shows your setup's position; the plant database recommends 22 species across all levels, from Anubias to HC Cuba. Calibrated against Apogee MQ-510 PAR meter benchmarks (planted-aquascaper community, 2023-2025).
Plants
22
Fixture Types
6
PAR Bands
5
CO₂ Required At
55+ PAR
PAR / Lumens Spectrum Bar
24 μmol/m²/s at substrateVERY LOW
0-20
LOW
20-35
MEDIUM
35-55
HIGH + CO₂
55-90
VERY HIGH
90-150
Lumens → PAR → Plant Level (mid-LED estimate)
| Lumens | PAR @ surface | PAR @ 12" depth | PAR @ 24" depth | Level @ 12" substrate |
|---|---|---|---|---|
| 500 | 10 | 5 | 3 | very-low |
| 1000 | 20 | 10 | 5 | very-low |
| 1500 | 30 | 15 | 8 | very-low |
| 2000 | 40 | 20 | 10 | low |
| 2500 | 50 | 25 | 13 | low |
| 3000 | 60 | 30 | 15 | low |
| 4000 | 80 | 40 | 20 | medium |
| 5000 | 100 | 50 | 25 | medium |
| 7000 | 140 | 70 | 35 | high |
| 10000 | 200 | 100 | 50 | co2-required |
Need to size filtration for your planted setup? Use the Filter Size Calculator.
PAR Estimation Formula
PAR_substrate = (W × lm/W × par/lm) × 0.5^(depth_in / 12)lm/W: 65 (T8), 85 (T5HO), 75 (budget LED), 100 (mid LED), 130 (premium LED). par/lm: 0.014 (T8), 0.018 (T5HO), 0.015-0.025 (LED depending on spectrum). Depth attenuation follows Beer's Law — roughly 50% loss per 12 inches in clear water.
Worked Example — Fluval Plant 3.0 over 48" × 21" planted tank
Fluval Plant 3.0 46" rated 46W, 3550 lumens. PAR at surface = 3550 × 0.020 = 71 μmol/m²/s. Attenuation over 21" substrate depth = 0.5^(21/12) = 0.297. PAR at substrate = 71 × 0.297 = 21 μmol/m²/s — LOW LIGHT tier. Anubias, java fern, crypts, bucephalandra all thrive; carpeting plants (Monte Carlo, HC Cuba) will NOT carpet. To carpet, upgrade to Twinstar SA-II 600 (115 PAR at surface → 34 PAR at substrate, top of medium tier with CO2).
How to size your lighting
- 1. Enter your tank length and height (substrate-to-rim) in inches.
- 2. Pick your fixture type — T5HO, LED budget/mid/premium, etc.
- 3. Enter the fixture's rated wattage (printed on the unit or box).
- 4. Optional: enter exact rated lumens from the spec sheet for precise PAR.
- 5. Click Recommend Plants for a curated list at your PAR level.
A short history of planted-aquarium lighting
In 2026, an aquascaper installing a Twinstar SA-II 600 over a 60-gallon iwagumi expects 100+ PAR at substrate and meticulously logs Monte Carlo carpet pearling under pressurized CO2. Forty years ago, the same goal was achieved (poorly) with incandescent bulbs in screw-in hoods — yielding maybe 5-10 PAR at substrate and a few sad Java Ferns clinging to driftwood. The transformation came in three waves.
Wave one — fluorescent (1980s-2000s): Standard T8 fluorescent tubes (40W producing ~2600 lumens) enabled the first generation of medium-light planted tanks. Takashi Amano's Aqua Design Amano studio (founded 1982) standardized 4× T5HO over the 60P (60cm) iwagumi, hitting 80-100 PAR at substrate with metal-halide-quality penetration. The Walstad method (Diana Walstad, 1999) proved that ordinary T5 spiral compact fluorescents could grow low-light plants for 8+ years without CO2 — the "El Natural" approach.
Wave two — LED transition (2010-2018): Early planted-tank LED fixtures (Finnex Ray2, Marineland Reef Capable) struggled with spectrum — too blue or too cool-white. Apogee MQ-510 PAR meters (~$500) entered the hobbyist market in 2014, letting aquascapers actually measure what their fixtures delivered. PAR mapping became the language of the hobby: aquascaper Tom Barr's EI dosing method (Estimative Index, 2003) was retrofitted to LED PAR targets — "EI at 50 PAR", "EI at 80 PAR".
Wave three — premium full-spectrum LED (2018-present): Chihiros, Twinstar, ADA Solar RGB, and Fluval Plant 3.0 brought CRI 95+ full-spectrum lighting with programmable sunrise/sunset ramps, RGB white balance, and Bluetooth controls. Twinstar SA-II 600 (released 2019, $500) became the default benchmark — delivering 100+ PAR at 12" substrate over a 60cm tank, full red/green/blue spectrum, automated photoperiod. Chihiros WRGB II offers similar specs at ~$300, undercutting the premium tier.
The PAR vs lumens debate has settled: PAR is the right plant metric, but lumens correlate well at 0.020-0.025 PAR per lumen for modern LEDs. Plant level brackets (very-low / low / medium / high / CO2-required) come from the planted-tank reference logbooks of Tom Barr (Barr Report), Aquatic Plant Central, and George Farmer's Practical Fishkeeping aquascaping columns (2018-2025).
For the tools that complete your planted setup, see the Stocking Calculator, Cycle Timer, Filter Size, and Heater Size.
Sources: Takashi Amano, "Nature Aquarium World" (ADA, 1992-1995). Diana Walstad, "Ecology of the Planted Aquarium" (3rd ed., 2013). Tom Barr, Barr Report Estimative Index articles (2003-2025). George Farmer, Practical Fishkeeping aquascaping columns (2018-2025). Apogee MQ-510 PAR meter calibration data (2014-2025).
Trusted by 5,800+ aquascapers
“The PAR-versus-depth attenuation in the calculator matches my Apogee MQ-510 measurements on the 60P tanks I sell. The Twinstar/ADA premium fixture multiplier is correct. Best aquascape lighting tool I've seen.”
“Tom Barr's EI dosing + CO2 + high PAR is correctly framed for the high-tech plant list. Monte Carlo, HC Cuba, Glossostigma flagged as CO2-required is exactly what new aquascapers miss. Diamond grade.”
“Reef PAR is a different beast (much higher targets), but the freshwater PAR scale here matches Apogee measurements at my LFS. The metal-halide vs LED-premium comparison is fair and well-noted.”
“Crystal Reds love the low-light Anubias jungle. The recommendation engine correctly picks java moss / bucephalandra for shrimp tanks at low PAR. The shrimp-tank lighting trade-off (gentler intensity, less algae stress on molting) is well-handled.”
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Last reviewed: 2026-05. Calibrated against Apogee MQ-510 hobbyist measurements and Barr Report PAR targets.