[StirCrazy]

Originally Posted by Shadetree

Steve,

Not to be the pessimist but isn't there one variable that will skew all the results, water turbidity (Is that the right word?). Unless the water in the tank is approximately the same age, with the same amount of water changes, comparable skimming and equal carbon use, comparing different tanks is like comparing apples to oranges. The readings above the water will all be pretty accurate, or multiple setups on a single tank would be good, but the different tanks with different water quality would play with the numbers too much. Testing each system individually for long term drop off values is quite handy though. If carbon can "polish" the appearance of tank water to the naked eye, how much does that effect the light penetration?

Scott

yes turbidity could skew results, I would guess that water that you can actualy see "organics/tannins/ect (would show up as a slight yellowing to the water) would only afect the readings by about 5% at the most.. and actualy solids floating in the water would be higher..

but having said that you can get a pretty close number in two different tanks if the other varables are simular.. I am not doing a sientific study, I am only comparing numbers to make it easyer for people to see the difference between bulbs in order to make a semi informed dission when buying lighting.

This was never intended to be a 10 million buck test, as I am not able or willing to start doing controled testing in lab like conditions
(nor can I aford it ) . I am going for aproimation which will be close for what I am doing, as for the most parts the difference in clarity of a well skimmed and maintained SPS tanks will be small. Weather I end up with a exact # or a number that could varry by 5 to 10% isn't a big deal as that will still be close enuf to make a informed choice, and to find the difference between bulbs.. Remember that brand new MH bulb vary by up to 10% in output from the factory

Steve