Well would like to start off as this is some findings that I have had with my 75 gal tank. The tank was started 10-19-08 paramiters are as stated ph 8.4 nitrate none nitrite none amonia none calicum 400 alk 9 dkh phosphates none detectable System includes sump with fuge that is a 29 gal long tank. I also run a coral life skimmer 125. Water movement is a 900 gph mag drive pump, yes I know this is low but the point is the lighting not water movement. So now to the point of the thread. one side of tank is lit with a odyseaa 250 w metal halide 15,000 k with 2 65 w antics the other is lit with a coralife 30 in. t5 unit with one daylight 10,000 k bulb and one antic bulb. Both lights were purchased around same time. there was probably a months diffrence though. On the t5 side the coraline growth is showing a very dense pattern of growth and the colors are showing more towards the pink side of the spectrum. This side seems to grow faster. you can see in above picture on back glass and black over flow the coraline growth. Coraline growing on over flow seems to grow more intense then on back glass. I wonder if this has to to with just general tempature or with color. On the MH side the corline growth is more sparce and leans more toward the purple or blue spectrum. Very slow growth. There is no overflow on this side so it is hard to make a decisive judgement on weather or not color has anything to do with growth or not. With these findings I am comfortable to say if you want to change your overall look of your coraline then you can do so by lighting. More growth/ pinker corline = less stong lighting Less growth/ bluer corline = more strong lighting Warning: If changing lighting you may experince corline die off and other coraline may need to take its place. These findings are soly based on my system set ups and parmaiters and if you want simuler results you may have to change many other factors other then just lighting. I hope all find this information usefull thanks for reading. please post comments on your systems corline growth and questions.