5.6ft 260 Gallon Hexagonal Wooden Norlog Koi Pond, 620mm high, (plus depth of sump underground)5. 6ft 260 Gallon Hexagonal Wooden Norlog Koi Pond, 620mm high (plus depth of sump underground) In stock for a 2 3 day delivery! With an added sump lower section to be dug under the ground especially for koi, they need deeper water depth when cold so the pond goes lower than the side walls, (this needs digging lower than ground level, see picture with dims), please ask if you need assistance with koi keeping as we have in house experts with many years