Plexiglass Lid

[Static]

I used 1/8th inch plexi on my freshwater tanks for a while, but they sagged bad, I'd suggest using atleas 1/4 or gluing on some supports to stiffen it up.

[Kabong]

I use plexi on my 50. So 2 1/8 pieces about 18" by 18".
It has a center brace so it only spans about 12" unsupported.
It does bow a bit but not to the point where it touches the water or anything.

If you got a dremel or a rotozip and a drill its simple to work with and you can custom cut it to exactly what you want. As well as cut out spots for filter's, light legs, cords.

[digital-audiophile]

Call me simple, but I use eggcrate to cover my aquariums.

[kari]

wet side = long side, hense the horse shoe piece of acrylic.

[Paverdude]

If you are in Calgary, there are a few aquarium makers to try
Who? links?