Bush snail on strange medium

[ajdamania2]

Hi all, yesterday I bought a den. Farmeri at the rhs orchid show and noticed some bush snails on the sphagnum moss. I thought I can get rid of the medium and the snails if I remove it all. However the sphagnum moss was on the surface and the roots were densely packed with some perlite and something like spikes of a sea urchin. Do you know what it is? Whatever it is ,it does hold lots of water and the roots look gone. What should I do?