The koi dome from vt has been a big hit with our customers recording 100% feedback!how it works simply place the dome in your pond then invert it whilst it is underwater. Once the dome returns to the surface the water that has collected inside it remains as a 'bubble'. Your fish can swim into this 'bubble' especially if tempted by some carefully positioned treats and you will see them appear above the surface of the pond.important you will need at least 50cm water depth to be able to get this unit to work successfully.