Wpg , How Would I Calculate ?

[Infidel_Uk]

watts per gallon ? im reading up on co2 and have hit a wall, i would like to work out how many wpg my lights are producing, is theree a website that can *do it for me* ?

i hope so !

 

[Bignose]

I don't delve into the planted section at all, but found out how many watts your lights put out and divide by how many gallons your tank is -- or is this too simplistic?

 

[cheesy feet]

I don't delve into the planted section at all, but found out how many watts your lights put out and divide by how many gallons your tank is -- or is this too simplistic?

That's it.
Although WPG has so many variables, making it inaccurate when comparing what others have.E.g depth of tank, type of bulb (standard t8/T5 HO etc).
It is generally considered 2WPG is required for a plant set up for good growth, though heavy root feeders like crypts can thrive on very little at all.

 

[OldMan47]

As Dr Honkerface said, the simple numeric average of watts per gallon is simple to derive for almost any situation. The problem that you run into is that much of the data was found using T-12 fixtures over a 4 ft long tank. Any other configuration needs to be adjusted for the light equivalence of this situation. The simple fact is that the T-8 and T-5 bulbs produce more useful light than a T-12 so the ratings are skewed by that. Furthermore, a light source of 50W over a 4 ft tank that is 2 ft deep and the same light source over a 2 ft long tank that is 4 ft deep do not provide the same amount of light to the plants. The plants don't really care how much light is wasted getting their light to them. The end result is that WPG is easy to calculate as suggested by Bignose but is not a very reliable of thinking about light for plants. A very small tank usually requires more light in terms of WPG than a larger tank would, for the very same plant. The real need is to measure how much light reaches the plant's leaves which is almost impossible to do. Instead we usually will say that a small tank takes a higher WPG value than a larger tank would for the same plant response. Some of the factors involved include light conversion efficiency of the bulb, geometry of the tank and light fixture and similar factors. Unless you are working with a T-12 bulb over a 55 gallon aquarium, the numbers are at best a rough estimate.

 

[loraxchick]

im curious...why would a smaller tank require a higher WPG than a larger one? that seems counter intuitive?
i have a 6 gal planted with what i think i high lighting with good spectrum and would really like to know.
and btw, my crypt is insanely out of control! the best plant (and oldest) in my tank...ive run co2 and dose with ferts, but would like some more info..algae is a prob in my tank and i cant have great filtration as there is an old very long-finned betta in there.
cheers!

 

[Infidel_Uk]

well i found a wpg calculator and here is my *result*

Size 99 x 41 x 46cm/39" x 16" x 18"
Surface area 0.40 sq m/4.33 sq ft
Current lighting 78 watts
Current intensity 193.8 watts per m2

but im using 2 t5 38 watt bulbs , im still confused because as has been pointed out these calculations dont take into account my type of bulb, grrr, lol

 

[aaronnorth]

there is no online calulator that takes into account the type of bulb,
you have 2wpg T5, which is plenty to grow any plant so long as CO2 & nutrients are up to scratch. I suggest you use pressurized CO2 and Estimative Index (EI) dosing for optimum results.
check out the planted aquariums resource centre (planted section of forum) for more details.

Loraxchick, wpg doesnt work on tanks less than 10gallons due to minimum light threshold, this explains it well, without me having to write loads on it

http/www.rexgrigg.com/mlt.html