How to Cut Plexiglass Lid when using Clamp Light?

[Guest]

So I am going tomorrow to buy a piece of plexi-glass to make a lid for the 55 that has been sitting in my garage for 7 months now. I also have a dome clamp light to use for heating. My question is - Should I make the plexi glass big enough to cover the whole top or should I have a hole cut out for the light to shine through? I don't want the plexi glass to melt so does any one know about how far up I would need to keep the lamp? Would it heat the tank enough if I had it over the plexi glass vs. having a hole where it could kind of sit in?

[Dramatic Hermiexx]

I'm assuming the plexiglas is going to be the thinner kind. If you're going to keep the lamp right on the lid, I would have a hole made (but make sure there are no uncovered areas where crabs can escape) in it unless it's a pretty low wattage bulb (a bulb or whatever your using on the 55 won't likely be considered low wattage though). This is only due to the possibility of the plexi warping, not heat blockage, it won't have much if any effect on how much heat enters the tank. If the light is going to be elevated, I wouldn't cut a hole, it may be an escape invitation if a decoration is very close to the opening. Elevation to avoid warping the plexi depends on the wattage (I would say about 6in for a 100w for example) and this and how the light is aimed at the tank effect how well the tank is heated. I would secure the plexi with some good quality velcro (or at least the back parts if it's split down the middle to be similar to a hinged lid) so it doesn't buckle into the tank and/or be pushed up but the crabbies; this is important if there will be a hole in it which will make the lid more likely to bend. If it's going to be a thick plexi, a hole is not necessary since it's harder to warp but some heat trasmittion will be blocked. I hope this isn't too confusing and it helps. I'm sorry that nobody replied any sooner.