Hi all, i was hoping anyone could help please - we are upgrading from a 4 foot marine fish tiank to a 5.5 foot and live in a purpose built 60's flat on the third floor. we have no idea which way the beams go or who made the floor or if it si solid concrete (thinking it must be given that the downstairs neighbours haven't ended up with a 4 ft fish tank in their lounge after 4 years!). We are really worried the floor just wont take it! Any advice please?