what are the corals coming from and going to?
On my tank I use 400W metal halide bulbs. after 10 or so months, the bulbs need to be replaces and show significantly less PAR and overall brightness. Conversely, new bulbs have a very bright period in the first two weeks that they are running. replacing my bulbs without altering my light setup would shock the corals.
People tend to do three things to alleviate these issues: 1) raise the lights 2) put a screen over the tank to decrease light penetration 3) reduce the photoperiod.
When I replace my bulbs, I cut my photo period in half and put two layers of window screen over the tank for about a week. I then remove one layer of screen and add 30 min to the photo period every other day for four days (adding one hour) I then remove the screen and add the light back 15 min a day until im back to my normal photo period. (a bit over kill perhaps but what isnt in this hobby)
When I'm adding new corals to the tank, I place them on the bottom of the tank for 5ish days. I then put them 1/3 of the way up in the tank, but at the periphery of the light cone generated by the halide. 5 days there. If the coral is to be placed at mid level in the tank, I move it to its proper place and glue it down. if it is to be place at the top of the tank, I move it to the center of the light cone where the light is the most intense for 5 more days. I then move it to its final placement.
