Heard of the 20-40W per sqft rule?

[brianclaw]

I can't remember where I heard this rule from, but it makes more sense to me than the WPG(watts per gallon) rule. Has anyone else heard this rule before?

[Aeon]

this?
http://www.fitchfamily.com/lighting.html

[Quixotic]

One of the URLs mentioned in that website leads to this, which mentions using square metres instead. Interesting samplings.
http://www.thekrib.com/Plants/Tech/Lighting/

[oblivion]

the guys from CAU base their setups on a 1W/L rule
how does that stack up against this?

[illumnae]

1W/L would roughly translate to ~4WPG wouldn't it, since litres and gallons can be directly converted, as opposed to surface area which can't be

[oblivion]

1W/L would roughly translate to ~4WPG wouldn't it, since litres and gallons can be directly converted, as opposed to surface area which can't be

yah i know. 1w/l about = to 4w/g
what i meant was how does this 1w/l rule stack up against the surface area rule?

[XnSdVd]

I'd say 1W/L makes more sense than 40W/sqft. The latter doesn't take into account the fact that many tanks are of varying depths.

[brianclaw]

I don't get it, how does the 1W/L make more sense? Let's take an 8 inch cube as an example. This container would hold 8 litres or 2.2 gallons, so using the 1W/L rule, you'd use 8W over the tank. Using the 20-40W/SQFT you'd have a range of 8.9W(we'll round it off to 9W) to 17.8W(we'll round this off to 18W).
Now if I were to go for a 48 x 24 x 30(H) inch tank -
1W/L would give me - 540W.
20-40W/SQFT - 160W - 320W.
I'd think this would make more sense. My calculations moght be slightly off, so feel free to correct me if they are, but I hope this helps make my train of thought clearer to anyone reading this.

[Shadow]

arg confuse, how about if the depth only 6 inches or maybe 36 inches? It is still the same number of square feet but is 320W too much for 6 inches depth tank or will it enough for 3ft depth tank?

[oblivion]

yeah i get what you all mean
confusing eh.
i guess both rules can't really cover all aspects so we have to add in some common sense here

i mean if your tank is 6 inches deep, the per sq feet rule obviously is gonna give you way too much wattage

[XnSdVd]

hence the 1W/L rule makes more sense. Since tanks are of varying depths.

[brianclaw]

i guess both rules can't really cover all aspects so we have to add in some common sense here

I think this makes much more sense then all the rules put together.

[oblivion]

I think this makes much more sense then all the rules put together.

i just do an agarration of the light needed and adjust as i see how the results go
not very cost effective but can't help it

usually it doesnt go VERY far off anyway and i try to compensate with adjusting the lighting period instead
better than changing lightsets every now and then!