Equipment Guides
How Much Light Does a Planted Aquarium Need?
How much light aquarium plants need in lumens per litre, why low, medium and high light differ, and how to avoid algae, with a free light calculator.
Read more →Aquarium Light Calculator
Recommended light
4,000
lumens
Approx. LED power
44 W
at ~90 lm/W
Lumens are a rough proxy; plants respond to PAR and spectrum. Run lights 6 to 8 hours a day to limit algae.
Estimate how much light your aquarium needs. Enter your water volume and choose a planting level to get a recommended brightness in lumens, from low-light setups to demanding planted tanks.
How much light does an aquarium need?
Planted aquariums are often sized by brightness in lumens relative to volume. As a rough guide, allow about 20 lumens per litre for low-light plants, about 40 for medium-light plants, and 60 or more for demanding high-light plants that usually also need added carbon dioxide. Lumens are only a proxy, because plants respond to usable light known as PAR and to spectrum, so treat the result as a starting point and adjust to how your plants grow.
Light needed by tank volume
| Litres | Low light (lm) | Medium light (lm) | High light (lm) |
|---|---|---|---|
| 20 | 400 | 800 | 1,200 |
| 40 | 800 | 1,600 | 2,400 |
| 60 | 1,200 | 2,400 | 3,600 |
| 100 | 2,000 | 4,000 | 6,000 |
| 150 | 3,000 | 6,000 | 9,000 |
| 200 | 4,000 | 8,000 | 12,000 |
| 300 | 6,000 | 12,000 | 18,000 |
Calculated with the same formula as the calculator above. Values are rounded.
Related calculators
Frequently asked questions
How many lumens does my aquarium need?
Allow roughly 20 lumens per litre for low-light plants, 40 for medium and 60 or more for high-light plants. Enter your volume and planting level above for a total in lumens.
Are lumens the best measure for plant light?
Lumens measure brightness to the human eye, while plants respond to PAR. Lumens are a useful starting guide, but PAR and spectrum matter more for growth.
Do high-light plants need CO2?
Usually yes. High light speeds up growth, and without added carbon dioxide and nutrients that often leads to algae rather than healthy plants.
How long should aquarium lights be on?
Most planted tanks do well with 6 to 8 hours of light per day. Longer photoperiods tend to encourage algae rather than more plant growth.
Can too much light harm my tank?
Excess light, especially without enough carbon dioxide and nutrients, is a common cause of algae. Reduce intensity or duration if algae appears.
Does tank depth affect lighting?
Yes. Deeper tanks lose light before it reaches the substrate, so a tall tank needs a stronger light than a shallow one of the same volume.
Related guides
Learn the core ideas behind fish tank volume before or after using the calculator.
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