Small Tanks Need More Watts Per Gallon?

[pentagon]

Trying to set up a small tank, 40cmx26x26, with 1.5ft 24w pl light.

Then read about this theory, it seems to say due to lights for small
tanks are less powerful (intensity?) comparing to lights for big tanks.

Compare to 60cm x 30 x 45H with 36W PL, is the small tank more suitable
for higher light plants?

[jiajuen900]

A smaller tank would require more watts per gallon compared to al larger tank, if both tanks are high tech. A tank of around 10 gallons would be better off with 5wpg compared to a tank of 30 gallons which would be good with 2wpg. This will be considered high light conditions in both setups.

But on why smaller tanks require more watts of light, im not sure. Maybe its due to more of the light intensity being lost in smaller setups.(more light shines out of the tank).

[comet]

Light is measure in lumens. How bright a light bulb is sort of related to the wattage it consume. Eg. 18 watt fl tube may produce a brightness of around 100 lumens (just a rough figure) and 36 watt may produce 150-200 lumens (just a rough figure). It depends on how the ballast is constructed as well.

If 36w of bulb is use on a 5G(1x1x1ft) and 15g(2x1.5X1ft) tank, both have the relative height, same amount of lumens brightness will hit the base of the tank. But if you work out the wpg, will be 7wpg and 2.4wpg. As you can see, height determine the light bulb intensity as well.

What actually matter most is the lumens, but not watt. Since we cant measure lumens without a photometer (a light measuring tool), aquarist use watts to estimate the brightness.

[Shadow]

To be exact, you need to measure PAR (Photosynthetic Active Radiation). Basically it is measure the amounth of light available for photosynthesis. In other word it taking spectrum into account.

[juggler]

There's something interesting to read here:
Lighting as a Function of Tank Size in the Aquaria of Takashi Amano