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 :wink: ) . 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

Scott, that is a good point. The differences between the bulbs tested over my tank I would think are fairly accurate, as my tank is pretty stable. Maybe we do need to measure turbidity with the PAR....

Steve, it is my wb+/-.. SO yeah, I guess it's just my white ballance. It has a meter:

Red---------I---------Blue

I just take it down 2-3 notches and it is prefect.. I find I don't lose blue where there should be blue.. I just sent brad a pic of his tank taken with those settings..

ahh ok ya with white ballance you won't lose color.. you are just finding the right ballance.. so I have to find the right setting is all then... could be fun LOL

Yep I think as long as you adjust it manually and not with a sheet of paper.

Digital cameras have given radiums a bad name!

naa sheet of paper is the best way but you can play with different color papaer for different effects hmmm gives me a idea....


Steve

Brad starts to worry...... :?

I have switch from 250 iwasaki to 400 radium on agro ballast 4 month ago and they are IMO the way to go for a show tank they have improve the color and still improve it each day at first I was tinking they were great but with time all the color shift from brown to solid puple,pink,blue....like crazy! The only coral that was looking more beautiful under the saki was a yellow plate so they are not great but amazing! for the grow I have not see any slower grow and I was with the saki for 2+ year the saki was only 6 month old when I have change for radium

I have try the m135 pulse start ballast and found it realy much more dim to my eye but no test have been done with PAR the color was looking similar but I could realy see shadow in the botom tank note that I have not try with a new bulb but only change the ballast on the old bulb. I have now turned back to the agro

I will keep people update for the bulb life but from now I have not see any noticable color shift or slower grow

Her is a good tread with different pic of collor change http://www.reefcentral.com/vbulletin...ghlight=radium

Hey Stephane, in all likelyhood, noticing a shift in color will be very very hard.. unless it is by comparing photos as a gradual shift will fool you (its like a friend who loses weight.. if you see him every day you don't realy notice it but if you see him only once a month it jumps right out at ytou.) .. now if you get what Brad just went through thats a different story and it still doesent make any sence whatsoever :D

Personaly I am thinking of buying 1 radium bulb to put in the middle of my tank.. on each side I will run the AB's I think that would be a real nice color ballance personaly, but I have to get thoes M80 ballasts first.


Steve