Planted Aquarium Lighting
Light is the engine of a planted tank, and the most common place people over- or under-buy. Choose a fixture by the tank's length, its water depth, and the plants you actually want to keep, not just by gallons.
What matters most
Match the fixture to tank length
Most aquarium lights are sold to span a range of tank lengths, either with extendable brackets or as fixed sizes. A light that is too short leaves the ends of the tank dim; one that is too long may not mount securely.
Account for water depth
Light intensity falls off with distance. Two tanks with the same volume can need very different fixtures if one is long and shallow and the other is tall. Deeper tanks generally need a stronger fixture to reach plants at the substrate.
Prefer adjustable output
Dimming and a built-in or external timer let you start conservatively and increase gradually. That flexibility is worth more than a high maximum output, especially in low-tech tanks without injected CO2.
Plan the mounting
Rimless tanks need brackets or hanging kits made for rimless glass; framed tanks may need legs that sit on the rim. Check the mounting style before anything else.
Check before you buy
- What is the tank's exact length, and does the light's bracket range cover it?
- How deep is the water from surface to substrate?
- Low-tech or injected CO2? Strong light without CO2 tends to invite algae.
- Is there a lid, a rim, or neither? Does the mount suit it?
- Does it have dimming and a schedule, or will you need a separate timer?
Your current light already covers the full tank length, reaches the substrate, and grows your chosen plants without persistent algae.
Ready to choose?
We have checked 10 plant lighting options for identity, specifications, and fit. Compare them, with what each needs and who should skip it, here:
- Best Planted Tank Lights for 48-Inch Tanks (55 and 75 Gallon) (2026) (buying guide)
- Best Planted Tank Lights for 10-Gallon Aquariums (2026) (buying guide)
- Best Planted Tank Lights for 20-Gallon Aquariums (2026) (buying guide)
- Best Planted Tank Lights for 40-Gallon Aquariums (2026) (buying guide)
- Finnex Planted+ 3.0 Review (2026): Specs, Fit, and Who It Suits (review)
- Fluval Plant 3.0 Review (2026): Specs, Fit, and Who It Suits (review)
- Fluval Plant 3.0 vs Finnex Planted+ 3.0: Which LED Fits Your Tank? (comparison)
Guides on this topic
Aquarium Light Intensity and Duration for Planted Tanks
How bright and how long to run a planted aquarium light: a conservative starting photoperiod, ramping up, siestas, and reading your plants and algae.
Floating Plants for Aquariums
How floating plants help a planted tank, common species compared, how they shade plants below, how to contain them, and why they must never be released.
How to Choose Planted Aquarium Lighting
Choose a planted tank light by tank length, water depth, mounting style, and the plants you want, not by gallons or watts per gallon.
How to Set Up Your First Planted Aquarium
A calm, step-by-step plan for a first planted tank: choosing the tank, easy plants, equipment, substrate, planting, cycling, and the first month.
Planted Tank Algae Troubleshooting
A calm, step-by-step way to identify common planted tank algae, understand what usually drives each type, and bring the tank back into balance.
Red Aquarium Plants: What Makes Them Red
Why some aquarium plants turn red, which red plants are easier or more demanding, and why reds fade to green or grow leggy in a planted tank.