The ground pumice I get ranges from perhaps 0.25 inch/0.5 cm (sorry can't find a ruler) down to fines. In most parts of the USA one cannot buy pumice with fines (i.e. dustlike particles), but I like it because I think it makes nutrients more available. Jane On 2/26/2017 1:06 PM, Mike Rummerfield wrote: > Jane, > In your seed mix, what is the size of your ground pumice? (e.g. > or < than > 1/8"/3mm) > > Thank you, > Mike >