thanks for your reply i wanted to keep my original gravel for my new tank (for bacteria ect) and i just wanted a new look on top and silica sand sounds perfectSilica sand is excellent as a substrate... try an inch or so over a gravel/Laterite mix... ideal if you are going with real plants...
All sand and gravel will eventually mix a bit due to fish burrowing and your own maintenance routines, so you may prefer to go straight to sand.