What Tazzy is trying to say is, get some fiber glass screen. Put up probably four layers over the tank, removing one each week. By four weeks everything should be gravy.

One thing, get some actual MH keepers advice first. I used this method when I changed over from PC to T5 like 5 years ago and worked fine. But not sure if this method is preferred with MH lights and the excessive heat the crank out.