Light Needed
23W
PAR Target
60
W/Gallon
0.5
Recommended Wattage
23W
1,840 lumens
PAR
60
W/Gal
0.5
$/Month
$0.66
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Inputs
Result
Surface area = 2.5 sq ft. At 12" depth, surface PAR ≈ substrate PAR. 60 PAR × 2.5 / 30 = 5W minimum, but with efficiency losses ~15W LED recommended.
Inputs
Result
Surface area = 6 sq ft. 20" depth = depth factor 0.35. Surface PAR needed: 115/0.35 = 329. Watts: 329 × 6 / 30 = 66W, plus efficiency = ~85W.
Low-light plants need 20–40 PAR at substrate level. Medium-light plants need 40–80 PAR. High-light plants (carpeting, red plants) need 80–150 PAR with CO2 injection.
| Plant Type | PAR Range | CO2 Needed? | Algae Risk |
|---|---|---|---|
| Low Light | 20–40 | No | Low |
| Medium Light | 40–80 | Recommended | Medium |
| High Light | 80–150 | Required | High without CO2 |
PAR (Photosynthetically Active Radiation) measures actual light energy plants use. Watts per gallon is outdated because LED efficiency varies wildly — a 30W LED can equal a 60W fluorescent.
Most planted tanks do well with 6–8 hours of light per day. Longer photoperiods increase algae risk without proportionally benefiting plants.
Yes. Water absorbs light exponentially. A 24-inch deep tank needs roughly 4x the surface light intensity of a 12-inch deep tank to achieve the same PAR at substrate level.
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Last Updated: Jul 24, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.