This water tank model is created in blender 2.8 and rendered with cycles engine.Here I've provided FBX, Obj/Mtl and also blender (.blend) file. 4K textures are used and provided herewith.
BLEND (Blender, filesize: 33.8 MB), OBJ (OBJ, filesize: 28.6 MB), FBX (Autodesk FBX, filesize: 15.7 MB)