I was skeptical at first whether this device can prove their worth. But I must say it's pretty accurate. I immediately my tap water tested, consistent with the waterworks. Although we have in Cologne extremely hard water of a conductivity of 760μs, but my shrimp tanks with active ground which, although exhausted, had water change 2 days ago and not fed and had a conductivity of about 1180μs, on the display stand 108 x 10 degrees. Came to me, although Spanish before, because I first tested it, but it's true. Without this device, I would grope in the dark. The device I can only recommend. However you adjusted to a longer delivery 2 weeks, even if supplied from Hampshire UK. This one has a cheap device that can compete with expensive loose. TOP !!!!!