Estimate a starting lumen range from aquarium volume and planting intensity.
Open live calculator →A 120 litre planted tank at 25 lumens per litre starts around 3,000 lumens.
A comparison starting point; depth, spread and plant choice matter.
Multiply net water volume by a selectable low, medium or higher-light lumen target to compare light fixtures.
The live tool updates immediately and shows the result in the units commonly used by aquarium keepers around the world.
Depth, spread and fixture optics affect usable light.
Increase light only with balanced nutrients and carbon availability.
Start with a controlled photoperiod and observe algae response.
Rough starting bands are 15–25 lumens per litre for easy plants, 25–40 for medium demand, and 40+ for demanding carpets—always balanced against CO₂ and nutrients. PAR data, when available, beats lumen rules.
Six to eight hours is a sensible starting photoperiod. Longer light without matching CO₂ and fertiliser mostly grows algae, not plants. Use a timer for consistency.
Usually an imbalance: more light than the CO₂ and nutrient supply can support. Reduce intensity or duration first—it is the easiest variable to control—then address CO₂ and dosing.