I have never used pumice. I actually prefer to use packing peanuts. I use the packing peanuts I get from mail order stuff in place of Perlite. I use it in the lower layers of the potting mix. I 'restart' a lot of rootless rhizomes of gingers and heliconias, and in the cooler parts of the year it is extra important not to have the soil retain water so rhizomes don't rot. I have used a mix of 1/3 peat moss, 1/3 orchid bark and 1/3 Jungle Growth (tm) potting mix with the extra addition of packing peanuts for years. It never fails me. I root plumeria in it too
