API CALCIUM TEST KIT Saltwater Aquarium Water 1-Count Test Kit

People debate the accuracy of this all the time when compared to the higher end test kits. For me, it simply works. The resolution of the testing is to 10 ppm and other products go .5 ppm. I'm personally okay with knowing I'm either 420 PPM or 410 PPM weekly. The point is to graph and understand the trend line over time. If you're trying to track specific daily fluctuation you're better off going with a higher end kid. For me it works and is simple to use for my application. Tip: 10 drops of Bottle #1 and shake. When you start bottle #2 you'll start seeing a trend based on your tank consumption. For my tank, I'm consistently at 400+ PPM. So for Bottle #2, I put in 19 drops at the same time and shake. Then add additional drops until I see the color change. Don't add a drop and shake starting at the beginning or you'll be there all day.

I initially purchased the API Freshwater Master Kit and used it for many years before moving into the saltwater side of the hobby. I then purchased the Saltwater Master Kit (which I found was no different than the Freshwater one, except for the results card) and have used it for over a year, testing my parameters when I see fit. Once you have an established aquarium, the need to check parameters is greatly reduced...thankfully. However, once I started adding corals to my tank, I began reading online about Alkalinity and Calcium and how critical they are for the growth and health of corals. At the time, I didn't think much of it and continued maintaining my tank as I did before. Throughout the first year of owning my tank I would encounter new situations, such as algae growth and corals being closed. The latter was a pretty big concern because I believed it meant my corals weren't "happy". I began searching for reasons why they might be closed up. I chose to purchase both the calcium and carbonate hardness (alkalinity) kits to test my water. I was surprised when my tank was right where it should be. In fact, EVERY time I have checked calcium and alkalinity levels they are fine. I would eventually find the real reasons why my corals were closed (one of which is that sometimes they just close for a day or two to "recharge") aside from a calcium and alkalinity imbalance. While these API products are great, I would recommend that unless you are keeping a huge tank full of corals, or are keeping a large amount of SPS corals, there's no real need to purchase the additional calcium and alkalinity tests. If you want to make sure all your parameters are perfect, they are good products, but for smaller tanks and hobbyists keeping softies and LPS corals along with doing regular water changes, save yourself some money and time on maintenance!

All of the API test kits are easy to use and reasonably accurate. I use several of their assays to monitor water quality in a commercial aquaponics farm. They are fast and as reliable as could be expected. The only concern with colorimetric assays like these is the subjectivity of the result, often the distinction between colors on the reference scale are slight and may be interpreted differently by different users. This calcium test, however, is one of the least subjective as the color changes very clearly from pink to blue. When I have sent water to university labs for comprehensive testing, the API calcium test result was always within 10ppm of the university result. Can't ask for much more than that for $7.

The end point color isn't an exact match to the color shown

This is a great test. It's easy to use and one kit will give you several months of tests. The test itself is very straightforward using a method called titration: add drops from bottle 1, shake, then add drops from bottle 2 until the solution turns from pink to the purple color indicated on the instructions. In-between drops from bottle 2, you invert the tube with the cap securely on. The more drops you need from bottle 2, the more calcium you have. You check the back of the instructions to translate number of drops to ppm. I have been keeping SPS, LPS, softs, and calcium-reliant macro algae in a small (25 gallon) system for some time with this kit and have had no calcium problems. As a quick tip: if you have multiple tests you run in beakers, get a 100cc syringe and attach some airline hose to the end. That way, you can fill the syringe with about 30cc of tank water and squirt it into each beaker to get the perfect amount in each (usually 5cc). No more dipping beakers in your tank and pouring some out, refill, pour out, refill, etc. Just put in 5cc directly and voila! Mine came with instructions and everything I needed. I have had no problems using this. Note that, the higher your calcium levels, the more drops from bottle 2 it will take and, thus, the fewer total tests you will get from this kit.

AP test kits work. I've used them for years and had no problems with getting consistent results. You do have to completely follow the instructions, and you need to read the results in daylight, not the LED or flourescent light over your tank.

It woks great easy to use

Calcium Testing kit instructions call for checking the water changing from pink to purple to blue.......my tanks all went pink to blue, but the only reference photo they give is a single purple square that never matched my colors.......the master test kit it awesome, but I'd pass on the calcium test, which were both the same price