If you can get a really coarse sand then it might work but most are really fine and as goldies like to forage then it can cause problems with the gills.
How are your fish doing with it Tokis?
I had sand in my goldfish tank for years. No offence BA, but that seems like nonsense to me. Otherwise all fish would have this problem, not to mention large cichlids who spend a lot of their time sifting sand.
In my opinion (and to an extent, experience) sand is better for goldfish as gravel has a tendancy to get stuck in their mouths.