ahh, still a bit large in my opinion but it can't hurt only help...
as for the Sand at home depot I have heard of a southdown play sand that is silica free you can use. I know that that particular line of sand is discontinued but the YardRight/OldCastle Tropical Play Sand can still be purchased in some locations which is reef safe I believe. try this link to find some locations or even call your local home depot to see if they can order it for you so they can absorb the costs of shipping.
http://www.crabstreetjournal.com/products/...alplaysand.html