Growth planning
Aquarium PAR Lighting Calculator
Estimate PAR at substrate, lux, light loss, and plant-light category.
- PAR zones
- Lux support
- Plant targets
Calculator
Tank, light output, and plant target
Calculate to classify the setup and see plant-light guidance.
Calculate to see carpeting guidance and a plant strategy.
- LSI Light Saturation Index style reference from substrate lux. It is a quick intensity signal, not a replacement for PAR.
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- Estimated volume
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- Light penetration Estimated percentage of light lost between surface and substrate after water clarity and depth are applied.
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- Water clarity
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- Model
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- Effective depth
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The curve shows light loss from the fixture toward the substrate, with subtle Low, Medium, and High PAR zones.
- Low: <= 30 PAR
- Medium: 30-60 PAR
- High: >= 60 PAR
Matched lights
Suitable lights for your setup
Suggested options based on your tank size and lighting setup.
Actions
Turn this lighting result into a next step
Open matching plants, save the setup for later, or export the result as an image.
Aquarium Lighting Calculator FAQ
What is a good PAR for planted aquariums?
As a practical guideline at the substrate: <= 30 PAR for low-light tanks, 30-60 PAR for most planted aquariums, and >= 60 PAR for carpeting plants and demanding species.
What does PAR at substrate mean?
It is the usable plant light that reaches the bottom of the tank. This value matters more than surface brightness because plants, especially carpets, grow and compete near the substrate.
Why can two LED lights with the same watts produce different PAR?
Diode efficiency, optics, spectrum, mounting height, and light spread all affect how much usable light reaches the substrate. Watts describe power consumption, not plant intensity.
Is W/L still useful?
Only as a rough reference. PAR at the substrate is more reliable because it accounts for tank depth, mounting distance, water clarity, and real-world light loss.
How does tank height affect lighting?
Taller tanks need more output because water depth reduces light intensity. Stronger fixtures, shorter mounting distance, or higher channel output can compensate.
Do I need CO2 if I run high PAR?
In most cases, yes. Higher PAR increases plant demand for CO2 and nutrients. Without matching supply, growth stalls and algae becomes more likely.
Why did algae appear after increasing light?
Light acts as an accelerator. If CO2, nutrients, or maintenance do not scale with it, algae gains the advantage. Reduce intensity or photoperiod first, then stabilize CO2 and nutrients.
Lux vs lumens vs PAR: what should I trust?
PAR, or PPFD, is the most plant-relevant metric. Lux and lumens help compare brightness, but they depend heavily on spectrum and do not translate directly to plant growth.