Introducing MH Lighting

[PeterW]

I am adding two 175watt MH into my 72gallon tank. I am planning to keep my 260 watt PC light in the front and the MH in the back of the tank.

What is a good way to introduce the MH into the tank without shocking the fish and coral? Anyone with experience?

I have a glass cover for my tank and was planning to keep it there to prevent salt water from getting on the MH. Is this a good idea or do people not like cover when they have MH lighting?

Thanks.

Peter