lighting question (halide)

[Marcs4020]

I currently have the double delux pc fixture which houses 2 x 65 watt atinics,2 x 65 watt 10k, and 4 lunars and i got the itch to get halides. i came across a 250 watt pendant and ballast combo that i was thinking of adding to my current setup. The way that i have it set up is with the tank being covered with two glass canopies that I can;t remove b/c they need to be under the pc's. The question that i have is can i use the halide pendant if it isn;t over uncovered water. What effect will the glass canopies have and is it worth it to get the halide.

thanks a lot,
Marcus

[SeanT]

Why does the glass need to be under the PC's?