I've recently bought a new LED light for my 200L / 4 foot long tank and started reading up on lighting for aquariums in general. (Will not be able to provide lighting specs but probably won't be super important for what I'm asking anyway).
Basically, I've found there is an 'ideal' amount of wattage per litre when it comes to sufficient lighting for plants HOWEVER, I can't seem to find anything on how to calculate the strength of light vs how deep down in the tank you go.
My tank is 40cm deep down, so if there is anyone who is able to shed some light
on the matter or even provide a means of calculation, would be greatly appreciated