If you decide to get the Psyllium, make sure you drink ALOT of water with it, otherwise if can cause more trouble then it's worth.
Also, be careful with products containing Senna or Cascara Sagrada. Excessive use of those two herbs can do very bad things to your colon. And if you suffer from any of the following, I would not take Senna or Cascara Products, at least not without talking to your doctor first
Irritable Bowel Syndrome
Liver or Kidney Disease
Blood Vessel Damage
Recent Colon Surgery
Personally, I would be more concerned with the Psyllium then the Bentonite Clay. Both can make you constipated without adequate water intake, but it just seems like more and more people (myself included) complain of Psyllium side effects, like worse constipation then before you started. But once again, BE VERY CAREFUL with Senna & Cascara Sagrada products. They can do alot of damage to your insides.
But the best colon cleanse, is just a good diet with lots of fruits and veggies. That's the best way to go.