My stout has zero head retention. My municipal water is untreated snow melt. I know you need higher alkalinity for big beers. Next time I'll condition the water before brewing. So what can I do now? Can I add something to the keg to help with head retention? I'm using CO2 not nitrogen, not ideal for stout, but I've been told by a couple of seasoned homebrewers that you can get decent head with CO2.