If you don't have a water feature that includes a pump you should be ok with that depth. It won't give you much leeway as far as having to remove excess water so the substrate does not sit in water. You will need to watch that. I have been giving mine about 2 inch's or more depending on the build. If you have a hight false bottom you can always adjust the water level in the pond by using gravel or stones to raise up the surface. If you need a deeper pond just remove some stones.