BerniceC:

I wish I could come and lend a hand to you. It's really not that hard. Just remember that concrete is porous and absorbs anything that goes on it. You could probably create your own artwork by throwing colorful foods, salsas, fruits etc...Let them sit. Wash them away. A splash of this, a blotch of that. No one will notice the algea...it'll just blend in. Candle wax also leaves a remarkable print. LOL