won't perlite fall though the pipes
 

I have built the 11 plant garden and I need some help. I know you need to use perlite, but where can I get some. When you put the perlite in the plant chamber, won't it fall though into the pipes, thus, won't the roots of the plants grow into the pipes also. I will be thankful for any help. Thanks.

Everybody sells perlite. K-Mart, Wal-Mart, Home Depot. Lowe's, and your local nursery. And use a painters strainer to hold it.