Hi Marius, I believe that there is nothing better to boost a new pond than mature media with colonies of beneficial bacteria on it.
The best would be to rather give him some of your mature media to get his system going, because if you place new media in your pond, it might take a few weeks for the bacteria to estabish on the media.
If you use for instance bioballs, exchange some with new ones. As far as I can remember, you are using matala. You could even give him a sheet of mature matala matting and he can replace it with a new one.
When he transport the biomedia, he should place it in a bag submersed with water to prevent the bacteria from getting dry. When I sell koi to a hobbyist that has a new pond, I normally give him some haircurlers and bioballs in a bag filled with oxygen.