Slider25,
A good clay will cause a colloidal suspension to permeate the water regardless the amount. Some of the clay will remain on the bottom of the tub which can be stirred up from time to time.
Clay or cloudy water in contact with the skin is what matters. It is more important that you remain comfortable, warm, relaxed, and fully submerged (except the head only occasionally of course) during a clay detox bath.
A good clay for detox bath purposes will also go down the drain without clogging the pipes. Most bentonites are swelling, clumping clays and should not be allowed to go down the drain. They are sure to clog the pipe and they are messy to clean up. Pyrophyllite, on the other hand, dissolves readily in water and will go down the drain just fine. A little spray or your next shower will easily wash any remaining sediment away without scrubbing. I have run 2 lbs of pyrophyllite down the drain on two occasions without a hitch.