Hi Tree Top. I have built a few aquariums. The main product I have used is acrylic. The last tank i built was plywood/wood, pond liner and then acrylic windows. It too was an 8ft long X 2ft wide X 30" deep. The acrylic was 2 - 2ftx4ft windows of 12mm or 1/2". Keep in mind acrylic is stronger than glass. I would suggest going with 3/4" glass for your application. The trick i found is sealing around the"window". I was able to drill through my acrylic to sandwich the liner like a port hole effect, along with a lot of silicone. i had bolts all the way around to tighten and make a good seal. This is going to be your weak spot too i would think. Being a wooden structure for the tank, it will flex somewhat, and you don't want the glass to flex obviously. Overbuild it and support it well! Don't be shy on the sealant.
lastly.....Good Luck!
Yeah, I got my 250w 14000k from Hamilton Tech. I think for $50. A couple years back I got the same from big Al's for $100.00 ea. Being an electrician, I've tried to get them through electrical wholesale or lighting wholesalers with no luck. I think it's because they by pallets of lights and it wouldn't be feasible for them to by specialty lamps.