That's because watts per liter or lumens per meter are irrelevant measurements. A decade or so it was the only guide we could use because PAR meters were (and to some extent still are) beyond the reach of most hobbyists and PAR was generally misunderstood. Any number used on a per volume basis is terrible because of the way light energy decays. The energy decay roughly follows the inverse square rule, so this means, for example, if you measure the energy at a certain distance from the bulb, the energy will be four times lower if measured at twice the distance. It will be nine time lower at three times the distance.How do you work out the watts per gallon for a set of lights?
I searched the forum but can’t find any info.
Yes, that is about right.So if I’m reading that correctly, 1 x T5HO needs to be just over 25 inches from the substrate to be in the blue zone?
Well this is the problem that arose as a direct result of the emergence of T5 bulbs in the 1990's. If you look at the T8 curve it was very forgiving and multiple bulbs could be used without any worry.My tank is only 16” deep. I’m struggling how to work out what I’d need to get going by that graph. Could you give me s pointer please?
It comes from the USA, the planted tank forum, member Hoppy:Any origin or source on that light chart
Is that just the 1 a160 you’re running on that rank?I've been running a 60cm x 45cm x 55cm (height) with a T5 fixture, finally switched (temporarily) to a Kessil A160 (the A360 would provide more even coverage if I were buying a light for this tank) & really prefer the access & dimming control etc, plants seem well enough though there are some shadowed areas that need to be taken into account- I adjusted hardscape etc