Joes Juice is prretty good. You can buy it from the website. It's a ton easier than kalk, or lemon juice or whatever. Bear in mind you can only kill what you can see, so typically you get a few more appear a couple of weeks later.
I can't imagine boiling water being any use at all. Kalk works, but you really have to inject it in with a needle, not just a syringe...