I have no experience with colonix, but can recommed oxypowder wholeheartedly.
Just eating a healthy diet and having a regular bowel movement doesn't necessarily prevent such disorders as diverticulitis. Your past easting habits or lifestyle may have contributed to formation of a consierable amount of bilairy stones in the bile ducts of the liver and perhaps also in the gallbladder. Their presence prevents enough bile to be pass through into the intestinal tract, thus impairing the intestine's ability to keep itself clean. Divirtulitis shows that to be the case. You may greatly benefit from doing a series of liver cleanses (see The Amazing Liver Cleanse, www.ener-chi.com). Follow the directions carefully (especially those concerning the colon cleanse after liver flushing), so as not to lead to any toxic side-effects. Using a magnesium oxide product may be helpful, but unless the orginal causes remain intact, the benefits may only be short-lived or not occur at all.