Hi Anne
My bog is attached to my pond and I use it to help filter the water, so I am not experienced with what you are asking.
If it were me - I would figure out what you want to plant first. Some plants like to have their feet wet - some plants like to be in a couple of inches of water. If you want plants that need to have their feet wet, I would think you would need to have some type of drainage in the tub. If you want plants that are to be in a couple of inches of water above the soil line, then I wouldn't think there should be any drainage at all in tub .
Thoughts?
