How To Calcate How Much Light My Fish Tank Needs in the USA

That all depends upon which plants you have chosen for your aquarium. If you have chosen nothing but “Easy” plants, 10-20 lumen (0.25 to 0.5 watts) per litre is adequate. For “Medium” plants, we recommend 20-40 lumen (0.5 to 1 watts) per litre, while “Advanced” plants require more than 40 lumens (1 watt) per litre….