Your nodes should not be on but in the pool. I.e. properly assign the nodes as child nodes for your pool node. To do so, select all the child nodes, press and hold SHIFT, drag the selected nodes into the pool, and finally release mouse button and SHIFT key. You can check if the gesture was successful by moving the pool node without having any of its child nodes selected. If the assignment was successful, the child nodes will be moved along with the pool node even though the child nodes are not selected.