It's not needed. Since most CPs are grown in trays of water. Not sure if it would poisonous to the plants either....

I actually tried this on my main Sarracenia purpurea a few weeks ago, mixed in a small amount of this stuff with a standard 1-1 peat-perlite mix. Used a bit too much, but it worked pretty well, I filled the soil to just under the ridge of the new pot, but as the soilmoist sucked in water it bulged, pushing up and out of the pot.

The effect actually worked pretty well, as it "cupped" the plant from underneath. I had to get rid of a small amount of soil to make watering it easier, but the plant seems to be happy, so it doesn't seem like it's poisonous to them. Probably useless though, to be honest -- I can't imagine it leeches out water fast enough to make any major difference, outside of maybe giving me an extra hour before the plants go from "dry" to "dying".

Still, the "cupping" effect was pretty neat, since my major problem with this S. Purpurea is that it's leaves get in the way of the soil and it's roots get left uncovered a bit.