Planted Tank Guru
Join Date: Jul 2008
Location: East Lansing, MI, USA
If the hydroton is locally stocked, and if you have a food saver, or one of those vacuum cleaner shrink bags, put the hydroton and water mix in a bag and pull a vacuum on the container. Air out - water in.
But... if it is something you have to order, one of the other suggested substrates would be easier to work with.