To clean sand.
Put it in a bucket or big bowl, take it outside and run the hose over it, stirring it up. Watch the water that comes out of the bucket when it over flows. When it is clear, stir up the sand and do it again. Keep doing this until you have clear water coming out and all the fine bits are gone.
Plants - you can leave them in their pots, but yes they can look silly. Carefully remove them from the pots and the mineral wool thats wrapped around the bottom. If you have a rooting plant, push it into the sand, and if you have a floating plant - well, let it float.
While there are no nutrients in the sand as Kris said, you will get some from your fish/plant waste. You may need to look into fertilizer or suplements if you want them to exceed.
GL.