Mobile Bay Reef Keepers

Switching form 3 each 250 watt 6.5Ks to 4 each 400w 20Ks. In your opinion, will there be a big drop in growth rate of the corals?

Thanks,
Jeremy

No.

I think a better question is will I be happy not having brown corals . I will see if I can dig up some PAR values for 400 watt 20kk bulbs. I think the par of a Iwasaki running on a M58 ballast is just above 700.

Growth rate does not matter if the color is not right. I would choose the bulb that you like for the color you want. You have to look at it all the time. Personaly I like 20k bulbs. but everyone is different. Your tank your choice..

Tar or electronic ballasts on the 400watters?
FWIW Generally better par but shorter life with electronic ballasts on the 20k... shorter as in 6 months.. Ouch!

tar

I always bought tar, the electronic are just too high.

I can't really find anything on PAR of a 400w 20k but there is an article by Sanjay Joshi and Dave Morgan comparing some 400w, 250w and 175w bulbs. He uses PPFD measurements for comparison. The 400w 20k Radium had a PPFD of 90.63 and the 250w 6500k had a PPFD of 124.3 on magnetic ballasts. I don't think that it will be much of a real difference because the 250w Iwasaki had a PPFD of only 90.7 on a Blueline ballast. Quality reflectors could increase the PPFD though, these numbers are without a reflector at all. You can read the results from his test here: http://www.personal.psu.edu/faculty/s/b ... rison.html

Thanks all for the information. I think I am gonna give it a try.

Jeremy

Here are some pictures I took comparing 6500k and 20kk bulbs. It really amazed me how much brighter the 400 is.

WOW, there is a huge difference. I did not think it would be that much difference.

Jeremy

LoneStar wrote:WOW, there is a huge difference. I did not think it would be that much difference.

Jeremy

Me either, that is quite a difference. Sorry about the coraline on the glass, it has been on a growth spurt recently.