Depending on how big your Uro is the following substrates should be used: (measurements are from snout to tip of tail)

If UNDER 7" Long - Newspaper, papertowels or butcher paper

If OVER 7" Long - Washed sifted play sand, millet seed or Pool Filter Sand

As for the coconut stuff, I'm not sure that would make a good substrate. I don't know alot about it. I only know what I have been told by others that have had Uro's for years.