The question is, what is your objective with the addition of peat? In sediments the sphagnum moss and peat are used as carbon sources to aid the development of the sediment bacterial colonies. So whether you use it or not depends on what sediment or sediment additives you are using. If you will use something like ADA Aquasoil then the addition of htese two products are unnecessary as the AS already has peat and organic matter included. If you are using an inert sediment like sand or LFS gravel by themselves then yes, adding organic matter like peat is a good idea but all you need is a sprinkling, not a kilogram of this stuff. If you are using an organic additive under the inert sediment then it's pointless.