💡 Lighting for Planted Aquariums – Complete Beginner’s Guide

If your aquarium plants are yellowing, melting, or just not growing — your lighting might be the problem. Whether you’re just starting a planted tank or upgrading from a basic hood, lighting is one of the most misunderstood parts of aquarium plant care.

This guide will walk you through everything you need to know about lighting for freshwater planted tanks: from light spectrum and PAR ratings to photoperiod tips and recommended fixtures. Whether you’re running a 5-gallon shrimp setup or a full-on aquascape, we’ll help you get your lighting dialed in for success.

🌱 Why Lighting Matters for Aquarium Plants

Plants use light to photosynthesize — turning carbon dioxide and nutrients into energy and growth. Without the right kind of light, plants can’t thrive, no matter how many root tabs or fertilizers you add. Good lighting supports:

• 🟢 Healthy leaf growth and color
• 🌿 Compact, bushy plant structure
• 💨 Efficient oxygen production
• 💧 Nutrient uptake (prevents algae blooms)
• 📉 Long-term tank stability

🎨 What Type of Light Do Plants Need?

Not all light is equal. Plants prefer a full spectrum that mimics natural daylight, specifically within the 400–700nm wavelength range — known as **Photosynthetically Active Radiation (PAR)**. Within this range:

• 🔴 Red light (620–660nm): Encourages flowering and root growth
• 🔵 Blue light (430–470nm): Promotes compact, bushy growth
• 🌕 Green/yellow (500–600nm): Mostly reflected, adds color balance

Look for lights that are labeled as “full spectrum” with a color temperature of **6500K** (daylight) for the best results in planted aquariums.

🔢 Understanding PAR – Not Just Watts

For decades, hobbyists talked about watts per gallon — but with today’s LED technology, **watts are meaningless**. PAR (Photosynthetically Active Radiation) tells you how much usable light reaches your plants at specific depths.

• Low light: PAR 15–30 (good for Java Fern, Anubias, Moss)
• Medium light: PAR 30–60 (Crypts, Amazon Swords, Val)
• High light: PAR 60+ (stems, carpets, CO₂-intensive setups)

Unfortunately, many cheap lights don’t list PAR values — and that’s a red flag. Brands that do (like Fluval, Chihiros, Twinstar, ONF, UNS) are usually worth the investment.

📏 Light Intensity by Tank Depth

Light weakens the deeper it travels. That means tall tanks (like a 20g High) need stronger lights than shallow tanks (like a 20g Long).

• 🔹 10″–12″ depth: Low-to-medium light will reach most plants
• 🔹 16″–18″ depth: Need medium-to-high PAR to reach the substrate
• 🔹 24″+ depth: Consider high-power LEDs or supplemental lighting

🕓 How Long Should Aquarium Lights Stay On?

Many beginners run their lights too long — thinking more light = more growth. In reality, too much light = more algae. A consistent schedule is more important than long hours.

• Low light tank (no CO₂): 6–8 hours per day
• Medium light planted tank: 8 hours/day
• High light, CO₂-injected tank: 8–10 hours max, with precise fertilization

Pro Tip: Use a timer. Lighting should be automated — not based on memory or guesswork.

🔦 Best Aquarium Lights for Planted Tanks (2024)

These LED fixtures are highly rated by the planted tank community and deliver excellent PAR, color spectrum, and long-term reliability:

• 💡 Nicrew ClassicLED Plus: Budget-friendly, decent for low-light plants. Add root tabs and ferts.
• 💡 Fluval Plant 3.0: Fully programmable, great PAR, smartphone control. Suitable for medium-to-high light setups.
• 💡 Chihiros WRGB II: Color-accurate, intense output, customizable. One of the best values in mid-high setups.
• 💡 Twinstar Light III: Premium spectrum and sleek design. Ideal for serious aquascaping.
• 💡 Hygger Full Spectrum LED: Affordable alternative with good red/blue ratios for low-tech tanks.

📚 Matching Light to Plant Types

Different plants need different lighting conditions. Here’s how to match your fixture to your flora:

• Low light (PAR 15–30): Java Fern, Anubias, Buce, Moss, Crypts
• Medium light (PAR 30–60): Amazon Sword, Vallisneria, Hygrophila, Rotala
• High light (PAR 60+): Dwarf Baby Tears, Monte Carlo, Red Ludwigia, carpeting plants

🌿 Do You Need CO₂ With High Light?

In a word — yes. The higher the light, the faster plants photosynthesize. Without enough CO₂ to match, they stall out, nutrients pile up, and algae takes over.

Rule of thumb: If you’re using a high-PAR light and growing stem plants or carpets, you need injected CO₂ or at least liquid carbon (like Seachem Excel).

🧪 Common Signs of Lighting Problems

• ☀️ Too much light: Algae blooms, especially green hair or black beard algae
• 🌫️ Too little light: Pale leaves, slow or no growth, melting stems
• ⚖️ Unbalanced spectrum: Plants stretch (leggy), poor coloration

Fix: Reduce photoperiod, reposition light, or upgrade to a better spectrum fixture.

🧼 Lighting and Algae – Finding Balance

Lighting alone doesn’t cause algae — but it plays a huge role. Algae thrives in unstable tanks with excess nutrients and uncontrolled lighting. To avoid outbreaks:

• Set consistent timer (6–8 hrs/day)
• Do regular water changes (25–30% weekly)
• Avoid overfeeding fish
• Keep plant biomass healthy and trimmed

🔗 Related Guides & Tools

• Beginner’s Guide to Aquarium Plants
• Fast-Growing Plants for Algae Control
• Fixing Common Plant Growth Problems
• Top Plant Mistakes to Avoid

📌 Final Thoughts – Lighting Is the Engine of Growth

Your planted tank lives or dies by the quality of its light. It doesn’t have to be expensive or complicated — but it does need to be intentional. Match your light to your plants, keep your schedule consistent, and monitor growth over time. If you nail your lighting, the rest of your aquascape will follow.

Need help choosing the right light for your tank size or plant goals? Drop your tank specs in the comments — I’ll give you a custom lighting recommendation based on your setup.