FWIW, I'm writing the review from the POV of a spa user. You can use this tester for your pool, salt water aquarium or your hydroponic planter. My supposition is, you're looking at this item because you have needs above and beyond test kits or simple test strips. With this pH meter (potential of hydrogen), you'll be able to quickly tell what your water's pH is. HM also has a total dissolved solid (TDS) meter, the COM-100, which I've had for about a week and absolutely love. The unit is waterproof, light weight, a bit smaller than the size of a small "C" cell flashlight or about the size of a large cigar. It's easy to use, easy to maintain, has a small form factor for storage purposes and once calibrated, I feel it's an accurate piece of test equipment that gives you the feeling of having control over your spa tub water chemistry. The unit comes from the distributor pre-calibrated. Batteries are included. A cautionary warning note, the sensor periodically needs to be replaced. The replacement sensor number is: SP-P2. Replacement is a simple process of remove, replace and calibrate. Delivered, the sensor runs about $45.00. Knowing the pH of your water is an important aspect of monitoring spa water chemistry. Without a pH meter of this kind, one won't have a dependable clue what their pH level is. Using test strips or a test kit, my experience, readings can easily be off by up to 1.1 pH. Having your pH out of whack can cause you to have the condition of your water being too acidic, which can damage your heater element as well as low pH can be hard on eyes and skin. If the water is too base, you'll have to deal with calcification/scaling/cloudy water problems which is hard on the tub, jets and plain yucky to get in. The alternative to this meter, test strips or test kits is having to take the time and regularly drop in to your local pool/spa supply house with water sample in hand, where they're going want you to spend more money. And I hate spending money on chemicals I might not need. This all so I feel good about getting my water tested for free. With this tester, that's no longer an issue. And If you're a bit geeky, enjoy the feel of accurate test data and like the peace of mind created knowing you have control over your water's chemistry, after using this tester a few times, you'll feel confident that you're finally in control of your water's pH reading. Yes, in my opinion, the PH-200 is a bit expensive but if you have the extra green, for the peace of mind and control over your water chemistry this tester gives you, you'll quickly come to the same conclusion I came to; money well spent. Why? Because this tester is da bomb. Note 1. Be sure to buy some calibration solution so you know your reading is accurate due to proper calibration. Calibration is simple. Holding the middle button in for a few seconds puts the unit in calibration mode. Place the meter in the calibration fluid and then fine tune the reading displayed in the LCD using the up/down arrows. In this case, for spa water, I use 7.0 pH calibration fluid. You want to use a calibration fluid that's close to your expected needs: 4.00, 7.00 or 10.00 pH. In the case of this tester, calibration is no more difficult than using a television remote control. Note 2. Amazon has calibration packets for sale and with distilled water from the grocery store, you can mix up your own calibration fluid. FYI, you will need to have something like a 100ml graduated cylinder on hand to accurately measure the amount of distilled water you'll need when you mix up a batch of calibration fluid. Also needed, is some "electrode storage solution" to keep the sensor bulb wet. No big deal to use. Put a half dozen drops of fluid in the protective cap that covers the sensor, place the cap on the tester like a pen and you're good as long as the tester is stored standing upright to keep the fluid inside the cap. This is a very sensitive measuring device. This extra effort is not as big of a deal as I make it out to be. Once you do the first time, you're good. And if you care about decent testing gear, you won't mind this bit of extra effort and you'll be glad you got one of these pH testers. Hope the above helps.
