Appistomaster, the top platform is a sheet of 3/4" ply backed with 4mm flooring underlay foam and then screwed directly into the concrete blocks giving a completely level flat base, the only reason the ply is even there is to iron out any slight bumps in the block work. On top of the ply sheet is 2" thick polystyrene sheet which again covers for any minor indiscrepencies and will help spread the load over the 5 block piers. The base of the tank itself is a hinged base (split in two parts with a silicon "hinge" and then a glass plate over the top of the silicon) which allows for any movement caused by the weight of the water settling, i have absolutely no doubts (well maybe some tiny ones but who doesnt with nearly 9000lbs of water)that the stand will hold the weight.
Seedy, i wont really need to get to the back for maintainance, i never clean the back or side glass of tanks as i believe that algea is an importent part of a tanks eco system and i only vacume the substrate if there is a real reason too such as uneaten food ( a rarity) or a fish has regurgitated, people try to keep their tanks too clean and as such never acheive a bomb proof thriving eco system, i change 20% of the water on all my tanks weekly and keep the mechanical filter media clean and thats what really matters. If i really do need to get to the back of the tank its on with the thigh length waders and in i get.
Kostas, i decided to leave the walls as they are for money saving reasons, with the reflective properties of the aluminum backed insulation i dont need to have the lights on during the day as the reflected light from the small window is enough to light the room. Our electric bills recently have risen to over £3000 a year so anything i can do to lessen this is a bonus (and means i can buy more fish). I am going to paint the backs and sides of the tanks however so the silver walls wont be visable to the fish.
Marc if youre ever in London then you are welcome to a visit, however i will set my electric eel on you if you touch my Auchenipterids
and i'm sure the only reason the mrs let me have the tank is the hope that i'll be able to keep something big enough to eat me one day
