Your sand will sink to the bottom of the eco-complete and not show over time, so if you are going to mix it you may as well not bother with the sand. I love pool filter sand, but if you want black sand try 3M color quarts sand. This place has free shipping. I have used this and it's beautiful! http://www.vbpstore.com/50-lb-bag-of-3m-color-quartz.html