Thanks, it is a first time for me! I am using the Fluval Shrimp stratum, even though it's probably not the best out there. Should look better when I get some water in and clean the rocks down a bit more and the substrate should compact a little.
People have said it is very messy stuff and breaks apart really easily. I haven't found it to be too bad really, but I haven't got it wet yet!
I am using a thin layer of 'JBL aquabasis plus' nutrient substrate underneath, just to provide an extra nutrient store for the plants.