Aquarium lighting is where more money is wasted than almost anywhere else in the hobby. Beginners buy cheap lights that look bright but don't grow plants, or powerful lights that trigger algae blooms. This guide tells you exactly what to buy for your specific setup, and what to avoid.
What Light Does in an Aquarium
Light serves two purposes: it lets you see your fish, and it drives photosynthesis in plants. A light that makes your fish look beautiful may do almost nothing for plants, and vice versa.
Understanding Light Measurement
- Lumen: total light output perceived by the human eye. Not reliable for plant growth
- PAR: the light wavelengths plants actually use (400–700nm). The correct measurement for planted tanks
- Kelvin: the colour of the light. 6500–7000K (daylight white) is ideal for plant growth and looks natural
Fish-Only Tanks: What You Need
If you have no live plants, almost any light will work. Choose based on aesthetics. A CRI above 80 will make fish colours pop. LED lights in the 6500–7000K range are ideal. Don't overspend here; a basic LED bar is perfectly adequate.
Planted Tanks: PAR Requirements by Plant Type
- Low light plants (anubias, java fern, mosses): 20–50 PAR at substrate level. No CO2 required
- Medium light plants (most stem plants, swords, vallisneria): 50–150 PAR. CO2 beneficial
- High light / carpet plants: 150–300+ PAR. CO2 injection required
LED vs T5: Which Is Better?
Modern high-quality LED fixtures now match or exceed T5 performance for planted tanks at a fraction of the running cost. LED wins on energy efficiency, lifespan (50,000+ hours vs 12,000 for T5), heat output, and programmability (sunrise/sunset simulation). T5 HO still has advantages for very large tanks (120cm+). For most freshwater planted tanks, a quality LED is the better choice.
Recommended Lights by Tank Size
Nano (under 40L): compact LED clip lights or small bars with adjustable intensity. Small (40–100L): mid-range planted tank LED bars with a dimmer, timer, and full spectrum. Medium (100–200L): quality planted tank LED fixtures; don't compromise here. Large (200L+): multiple LED fixtures for even coverage, or T5 HO strips.
The Biggest Lighting Mistakes
Running lights too long: more hours does not equal more growth. Plants photosynthesise for roughly 8 hours then stop. Running lights 10–12 hours just feeds algae; use a timer and stick to 6–8 hours. No ramp-up: sudden full-intensity light causes algae; use sunrise/sunset simulation. Buying on lumens: PAR is what matters, not lumen count. Wrong spectrum: high blue content (10000K+) promotes algae in freshwater; 6500–7000K is optimal.
Essential Accessories
- Timer: non-negotiable. A consistent photoperiod is essential for plant health and algae prevention
- Light hanger / suspension kit: raises LED lights for better spread on open-top tanks
- Light guard: prevents jumping fish from landing on hot fixtures
Browse our full range of aquarium LED lights, timers, and lighting accessories in our Lighting range.
