UV Light Good/Bad

[Bblinks]

I don't know if this will help, I have a glass shield on my 400w mh with a glass top. last month I decided to take my glass top off so I don't have to clean my glass top all the time.(I am not lazy just try to make things easier ) I had the glass off for about three days and all of sudden 5 of my acros started to bleach. Now I am not sure if its due to the sudden change in light intensity and excess uv shinning down but I immediately replaced my glass top, 2 weeks later 3 of the 5 recovered and the other 2 is now in the garbage. I don't believe that coral needs uv to grow but it can definitly with stand it and flourish either way. What I am trying to say is take it slow, raise your light and let your coral get use to it and not just remove it like I did. best of luck let me know how it turns out.