Hi guys,
Lighting for tanks are quite complicated and we can only quote experts who post articles or from things we read.
This is always too much info for the average hobbyist.
So the WPG guide came about to simplify matters. [Whoever the inventor is] this is what i take it to be for planted tanks: <2 WPG is low, 2-3 WPG medium 3-4 high >4 super high
In actual fact this is just a rough guide assuming that using FL lights with ordinary reflectors and standard 18" high tank with reasonably clear water. [not blackwater setup!]
WPG guide becomes very inaccurate for tanks below 25G. Smaller tanks would seem to have like ~8WPG when it has only 2X15WFL on a 4G.
For bigger tanks above 125G it also dips in accuracy a little.
eg a 2WPG for a 200G is 400W of lighting. [which is actually moderate to high in actual plant growth/speed terms.]
The more accurate measurement would be total W/surface area with due consideration to height of tank, water clarity, surface scum, reflectors etc.
some definitions on Lux.
The lux (symbol: lx) is the SI unit of illuminance. It is used in photometry as a measure of the perceived[what we see] intensity of light.
Caution though, we may look at a bulb and think it's very bright but what the plants uses may not be in that range it's emitting.
The important wavelength of light needed by plants are in the PAR[photosynthetically active radiation]
so specially made bulbs are presumed to have this incorporated. So we get pay a premium for these tweaked bulbs.
So wanting to have lasting power in this hobby means finding cheaper ways to do things.
Imagine changing 20tubes yearly at average 60 bucks per tube? pock kai man.
In conclusion so far the new shop bulbs works.
The CRI[colour rendition index] looks good and is only a fraction of the cost.
That said, I still buy the 'designer bulbs but mix and match them.
Regards
Stan
|