a heliamphora island on the tepui
very interessant like substrat , no?
have you use 'akadama' (bonzaï clay) in replacement to 'seramis' ?
on the tepui no problem with the sandstone ,the granit in mix to carex peat , no problem with iron also very present up there.
but attention with the copper very harmful , in the substrat or in the aerosol bomb or fertilizer.
have you with the perlite some dissolution problem with the water ?