What is PAR and Why Does It Matter?
If you're serious about growing healthy aquarium plants, you've probably heard the term PAR thrown around. But what exactly is PAR, and why is it so important for your planted tank?
PAR (Photosynthetically Active Radiation) measures the amount of light in the 400-700 nanometer wavelength range that plants can actually use for photosynthesis. Unlike lumens or watts, which tell us how bright a light appears to humans, PAR tells us how much usable energy your plants are receiving.
Think of it this way: a light might look incredibly bright to your eyes, but if it's not producing light in the right spectrum, your plants won't benefit. PAR is measured in μmol/m²/s (micromoles per square meter per second) and is the gold standard for evaluating aquarium lighting.
PAR Requirements for Different Plant Types
Not all aquarium plants need the same amount of light. Understanding PAR requirements helps you choose the right lighting intensity:
- Low-light plants (30-50 μmol/m²/s): Anubias, Java Fern, Cryptocoryne, Bucephalandra
- Medium-light plants (50-100 μmol/m²/s): Amazon Swords, Vallisneria, most stem plants, Rotala
- High-light plants (100-200+ μmol/m²/s): Carpeting plants (HC Cuba, Monte Carlo), red plants, demanding stems
Too little PAR means slow growth, leggy stems, and poor coloration. Too much PAR without proper CO₂ and nutrients leads to algae problems. Finding the sweet spot is key.
How PAR Decreases with Depth
Here's something many aquarists overlook: PAR values decrease significantly as light travels through water. A light that delivers 150 μmol/m²/s at the surface might only provide 75 μmol/m²/s at 40 cm depth.
This is why:
- Deeper tanks need more powerful lights
- Carpeting plants at the bottom need higher surface PAR
- You should measure PAR at substrate level, not at the surface
Choosing the Right Light: Premium Options for Every Tank
When selecting an aquarium light, PAR output should be your primary consideration. Two brands stand out for their exceptional PAR performance and build quality: Chihiros and Skylight.
Chihiros WRGB2 Series: The Gold Standard
The Chihiros WRGB2 series is specifically engineered to deliver exceptional PAR values across all tank depths.
What makes Chihiros WRGB2 special:
- High PAR output: Delivers 100-200+ μmol/m²/s at substrate level in standard tanks, perfect for demanding plants
- Full spectrum coverage: WRGB (White, Red, Green, Blue) LEDs ensure complete 400-700nm coverage
- Adjustable intensity: Dim the light to match your plants' needs and prevent algae
- Even distribution: No dark spots or hotspots in your tank
- Energy efficient: High PAR without excessive power consumption
Available in multiple sizes:
- Chihiros WRGB2 Slim 30 cm - Perfect for nano tanks
- Chihiros WRGB2 Slim 45 cm - Ideal for small planted setups
- Chihiros WRGB2 Slim 60 cm - Most popular size for standard tanks
- Chihiros WRGB2 Slim 90 cm - For larger aquascapes
- Chihiros WRGB2 Slim 120 cm - Professional-grade for display tanks
For deeper tanks or maximum PAR output, consider the standard WRGB2 models:
Skylight Hyperspot F: Precision Lighting Control
For aquarists who want ultimate control and cutting-edge technology, the Skylight Hyperspot F LED from Skylight offers WiFi connectivity and exceptional PAR output with pinpoint precision.
Skylight Hyperspot F advantages:
- WiFi control: Adjust intensity, spectrum, and schedules from your smartphone
- Focused beam: Concentrated PAR delivery perfect for high-tech aquascapes
- Premium build quality: German engineering for long-term reliability
- Customizable spectrum: Fine-tune red, green, and blue channels independently
PAR vs. Kelvin: Understanding the Difference
Many aquarists confuse PAR with color temperature (Kelvin). Here's the distinction:
- Kelvin (K): Describes the color appearance of light (warm vs. cool). A 6500K light looks neutral white, 8000K+ looks bluer.
- PAR: Measures actual photosynthetic energy, regardless of color.
You can have a 10,000K light with poor PAR, or a 6500K light with excellent PAR. For plant growth, PAR matters far more than Kelvin rating. Both Chihiros WRGB2 and Skylight provide optimal PAR with a natural 6000-8000K appearance that makes your plants and fish look stunning.
Balancing PAR with CO₂ and Nutrients
High PAR is only beneficial when matched with adequate CO₂ and fertilization. This is Liebig's Law of the Minimum in action:
The PAR-CO₂-Nutrients Triangle:
- High PAR + Low CO₂ = Algae problems
- High PAR + High CO₂ + Low nutrients = Stunted growth
- High PAR + High CO₂ + Balanced nutrients = Explosive plant growth
If you're running a Chihiros WRGB2 or Skylight at full intensity, make sure you're injecting CO₂ (aim for 20-30 ppm) and dosing a complete fertilizer like MasterLine regularly.
Practical Tips for Optimizing PAR
1. Start lower and increase gradually: Begin at 50-60% intensity and increase over 2-3 weeks as plants adapt.
2. Use a photoperiod of 6-8 hours: Longer lighting doesn't mean better growth—it often means more algae.
3. Measure at substrate level: If possible, use a PAR meter to check actual values where your plants are growing.
4. Adjust seasonally: Plants may need slightly more PAR in winter when growth slows.
5. Consider tank depth: Tanks deeper than 45 cm benefit from the higher output of the standard WRGB2 over the Slim version, or the focused beam of the Skylight Hyperspot F.
Conclusion: PAR is Your Plant Growth Foundation
Understanding PAR transforms you from guessing about lighting to making informed decisions. It's the difference between struggling with algae and melting plants versus achieving lush, vibrant growth.
Whether you choose the versatile Chihiros WRGB2 series or the precision-engineered Skylight Hyperspot F, investing in quality lighting with proven PAR output takes the guesswork out of planted tank success.
Ready to upgrade your planted tank lighting? Explore our complete aquarium lighting range and give your plants the light they deserve.