Hello again,
And thank you for your kind words of welcome. I think i've got the underfloor support sorted. I climbed under there a few times and put an extra five, 6 or 8 inch posts under the bearers. The architect when I quized him said put two so I think five should do it but I still feel nervous. The posts are supported on concrete squares and nailed to the top, correctly I think. The floor itself however is 20mm particle board so the stand, whether it's timber or steel, whatever, will have to have some load spreading qualities to the design.
The tank is 1800L x 600W x 630Deep, it's huge. The glass is 10mm but for the back for some reason which is 12mm. I missed out on a complete set up, 4ft x18inch x 18inch tank, stand/cabinet and everything else but fish on trademe and got this one on the rebound. I'll keep you posted.