Whether you're a beginner or an experienced aquarist, one question always comes up: How much light does my tank really need? And more specifically: How many watts should my LED light have?

Let’s clear things up – simple, modern, and 100% LED-focused. No outdated fluorescent tubes here!

Why "Watts" Aren’t Everything Anymore

Back in the day, the rule of thumb was: 0.5 to 1 watt per liter of water. That made sense for old fluorescent tubes – but LEDs have changed the game. They produce more light with much less power.

So nowadays, the important thing isn’t just the wattage – it’s the lumen output.

The Modern Rule for LED Aquarium Lighting

For a healthy, well-lit planted tank:

20 to 40 lumens per liter of water

This covers everything from low-light setups to tanks bursting with lush, light-hungry plants.

Example: How Much Light Does a 100L Aquarium Need?

Say you have a 100-liter tank with medium plant growth:

  • 30 lumens × 100 liters = 3000 lumens

  • Good LEDs produce about 100 lumens per watt

  • 3000 lumens ÷ 100 lumens/watt = 30 watts

So, a 30-watt LED with 3000 lumens is just right.

What Affects Your Aquarium’s Light Needs?

Not every aquarium is the same. Factors include:

  • Tank height: Deeper tanks need stronger lighting.

  • Plant types:

    • Low-light: Anubias, Java fern

    • High-light: Glossostigma, red plants

  • Natural light: A sunlit room can reduce your lighting needs.

  • Lighting duration: Aim for 8–10 hours per day.

Pro Tip: Always Check Lumens, Not Just Watts

When shopping for LEDs, don’t rely on wattage alone – check the lumens. That’s the best way to know what your aquarium is really getting.

Every LED bar in our shop clearly lists the lumen output – so you can choose with confidence.

Summary

With high-efficiency LEDs, less wattage is more. Use the guideline of 20–40 lumens per liter, match it to your plants, and your aquarium will thrive and look stunning.

Browse our LED lights now and let your aquarium shine!