One of my tanks has beach sand that was collected from a local beach. I just rinsed it a few times really well to get all the salt out and then dried it out in the sun before using it. I use it in my loach tank.
i use normal sea sand that i collect from a high dune at the local beach...coz its a high dune it has no visible impurities...i just add it straight in no problems so far! the up side of it is that every 3 months i just scoop it up put it in my back pack an go "exchange" for clean substrate...I'm that lazy!!