I have taken Oxypowder . I really like the effects - it's similar to taking aloe vera capsules (which also go through and turn everything to moveable liquid/solid in that especially sort of violent way hee hee). I use Oxypowder at home, and am going to start having colonics every 6 months.
Colonics serve a purpose that none of the supplements can match (though I haven't tried psyllium husk). Here's an analogy - if you've got a glass with some juice residue, pretty nasty, been sitting out for a few days, all gunked up.
A colonic is like washing the glass out repeatedly with running water. It's like a rinse. It's going to get clean if you have the right pressure and temperature of water.
Supplements are like trying to clean that glass with metamucil. you take this gritty stuff and put it into a gunked up glass and hope to get everything out. Now some of the experts on this blog will probably think this is an oversimplified metaphor, but it's how I think of things. Of course the Oxypowder , and aloe vera and all the supplements react with the stuff that's not moving in your intestines, making it easier to pass.
A colonic, when properly administered, gets water into the reaches of your intestines, gets that water around stuff that's stuck with gentle massage, and immediately gets it out. You do this multiple times in a single session. And most of the time they recommend you do two or three colonics over the course of two weeks or so. The massage part also really helps loosen things up, combined with the water, it's great. Maybe it doesn't feel great while you're doing it but the results are heads and shoulders above the supplements.
All I know is that after my first colonic I came out of what I considered a pretty uncomfortable experience literally glowing. My skin was glowing. You can't beat semi-pressurized water fills and releases administered by a professional. That professional is also watching closely what comes out and can give you feedback on what you're releasing, whether it's old or new build up.