I agree with all Jeff said, NONE of my BRB's has it's own light, just ambient room light from the window.
SCREECH.... (sound of old soap box being drug out)
From your post I'm envisioning a screen topped fishtank with a light bulb on top. IMO those are not the proper enclosure (as-is) for any BRB. They have two significant problems both of which can be band-aided and made to work..
1) The screen top lets all the humidity out.
Fix - cover most of the top with some sort of vapor barrier. Plastic, aluminum foil etc. Only a very small vent area is required. Play with it to get some condensation on the glass.
2) Glass tanks do not hold heat well. Glass being a good conductor of heat will wick all the heat out of the warmer enclosure into the cooler room. Forcing you to add more heat (also contributes to the tank drying out
fix - insulate three sides (and top if possible) to retain the heat.
Only trying to be helpful as I have seen MANY posts and talked to MANY people about why their BRB's are not doing well and that style of caging comes up in the discussion more often than not.
CLUNK (sound of old soap box being put back away)
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
26.49 BRB
20.21 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

