i have a large accumulator tank (300l) which when full will be approx
350kg. what should i do to strengthen the floor where it will stand.

at the moment the floor is 7"x2" joists resting on bricks on the solum
about a metre apart (so its not really suspended). the joists are at
450mm centres. at the moment the tank (empty) is on 18" ply which
spans 3 joists.