oops, i posted on the link thread. heres a copy for our club too. im sure someone might have more to add.
well, you now have about the same amount, or at least wattage of light over half of the tank, that you used to have over the whole tank. I take it that was your 96 watt PC and T5 hood to the right, on the floor.? so intesity is one difference. but there looks like a big change in spectrum/ the 150w DE halide looks like probably a 20,000K lamp. which is bluer and less intense visibly.
when intensity and spectrum change abruptly, the zooxanthelea have to change their mix to adapt to the new spectrum. so it takes time. there are a broad range of zooxanthelea in coral polyps all the time. but the ones that best use the predominant spectrum become the most abundant. change the spectrum and some will die off while the other minority types will have to multiply to take over the job. brown coral for a while.
or thats the theory i have read somewhere.
opinions vary. but you did make a big change. expect a reaction.
