If it is 10mm glass then the glass required to build is of a much greater quality and density/strength than most other glass. Speak with your local glazer for the type of glass you will need,it will definitely have to be a form of laminated toughened glass made specifically for fish tanks. As I said many manufacturers subject that tanks to an myriad of tests in order to be able to guarantee against failure. To be honest you are probably better off buying large tanks from somebody like NDAquatics or similar. At least if it breaks you have a certain amount of piece of mind if it does leak, as well as your insurance not being voided. My 72 x 26 x 26 tank is made of 12mm glass and double based, meaning there is a second plate of glass inside the tank laying on top of the base giving more strength. This is how a lot of the better quality tanks are built. Just as an idea the tank was £1300 new.

I wouldn't go with wood as that was a very old technique when glass was inhibitedly expensive in the very early days of fishkeeping, and wood is notoriously hard to stop warping and loosing its shape etc. Again a plywood or timber tank could cause problems with your home insurance as it is not a known factor they would be able to quantify and any damage caused by a wood tank failing would more than likely void any claim. Insurance companies would use any excuse not to pay out, so be very very careful.

Thanks, I've spoken with ND Aquatics and they use standard float glass with aquarium silicone - so nothing special there.

I do have the use of a garage, so I can at least have it set up there for a few weeks or even months - no rush, to test the water tightness/quality.

In the meantime Im in talks with a local glass supplier, and will do a big of digging in terms of home insurance.
Food for thought, but I can at least have a go making a 4ft or so one to get the feel for it.

In terms of the plywood method, there seems to be a lot of people who use this still with epoxy resin, fibreglass and braces. I have experience using fibreglass too after restoring a boat so I'm confident in the application.

Something to think about for now.

acrylic over took glass prices several years ago, but if you dont have to view the tank from the sides then i'd look into a fibreglass container with an acrylic front panel bolted in with a silicone seal

Now that is a very good idea Dragon, never thought of that. Working nights does fry my brain somewhat.

A great idea but the price of an 8x2 acrylic sheet over here thick enough for that is £950. Ridiculous I know!

Overall I feel a properly made plywood tank would be stronger and more secure. The issue though, is the weight.

Look at monsterfishkeepers, they swear by plywood tanks. I've plenty experience working with fibreglass so I have no doubts on the seal.

My concern is the weight, over 200kilo before water.

That is the big problem with large tanks, weight. The water in an 8 x 2 x 2 is going to come in at over 800kg, and that is a lot of pressure inside the tank walls. All in all the complete weight of tank and water is in excess of 1 tonne, add to that any stand you may want, that in iself is going to need to be pretty substantial, and the weight increases again. I hope your floors are nice and strong...!!!!