I don't think it will mess anything up but you have to add the sand very slowly over the next few days. If you add the sand all at once your tank may get coudy irritating any corals. Also be sure not to cover anything up like any corals or poylps, and if you have any corals don't get sand on them, this irritates them. Since the sand is so fine I would suggest putting some in a cup and pouring it very slowly to the other sand.