My EC meter tells me the water in the tank is at 20ppm. The tap water is often 10ppm or so. I figure the equipment I'm using might have had some dirt on it or something. Or possibly the Dechlorinator added an extra 10ppm. It could actually be 11ppm, but my meter always rounds up to the nearest ten. Is this a concern?

Also, my second question wasn't what could I grow in it, but when can I start growing veggies in it? Do I need to wait for the water to smell a bit?