Aquarium Lighting Calculator
Estimate lighting needs for low, medium or high-tech planted tanks.
How it works
Modern planting uses PAR rather than watts. As a guide: low-light plants need ~15-30 PAR, medium 30-50 PAR, high-light/carpets 50+ PAR at substrate. Photoperiod of 6-8 hours suits most tanks; longer periods invite algae.
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Formula & Method
Modern planting uses PAR rather than watts. As a guide: low-light plants need ~15-30 PAR, medium 30-50 PAR, high-light/carpets 50+ PAR at substrate. Photoperiod of 6-8 hours suits most tanks; longer periods invite algae.
Example Calculation
For a 45 cm deep tank growing a carpet, you'll want a quality LED delivering ~50+ PAR at substrate, run 7 hours daily, ideally with CO2.
Frequently Asked Questions
How long should aquarium lights be on?
6-8 hours a day for planted tanks. Extending the photoperiod usually fuels algae rather than plant growth.
Is the watts-per-litre rule good for LEDs?
No. LED efficiency varies hugely; use PAR ratings or manufacturer plant-level guidance instead.