As these are bulbs I am growing, they need more food than cacti do. And it is not rot, but disease which is the problem. Like you we have cold, wet winters, but not freezing, Shmuel. So I look for drainage and with feeding. Tomorrow I will go past the place which sells all these things and investigate further. According to their website the 7 mm pumice is supposed to be from 4-7mm. I don't see that fitting in with the sand and small stuff there is in this pumice. Ina On 2/07/2013 7:12 p.m., Shmuel Silinsky wrote: > I use fine as well as small pumice (I think that's what you would call it - > here it is called tuff) mixed with sand and a bit of sandy soil(sold in > bags here) in my inorganic cactus mix as well as for Atacama bulbs and > other that rot easily. (We have cold wet winters, but not freezing.) I also > use the fine with sand for germinating seed of drainage loving plants with > good success. > \ > Shmuel > Jerusalem Israel > Zone 9 -- Ina Crossley Auckland New Zealand zone 10a