You do not want to use test strips. They are junk. Buy the drops.
As for calcium, I personally test for calcium in all my marine systems. As the major buffering ion in seawater, calcium is such an important measure of the overall stability of a system that I can not imagine any argument for not testing it. By testing both alkalinity and calcium at the same time, you get an amazing picture of future problems that could occur and are able to make adjustments long before these problems arise.
In addition to the test kits, you will need a buffer and a calcium supplement. I use Kent Marine Super Buffer DKH and Kent Marine Liquid Calcium (calcium chloride). I keep alkalinity between 8 and 12 DKH and calcium between 420 and 460ppm.
Generally, you will see alkalinity and calcium "move" together, and adding both a buffer and calcium supplement will be routine. You will also develop a routine for a dosing of calcium to keep calcium above 400ppm, as it tends to drift down quickly, based on the effectiveness of your skimmer at removing the organic acids produced by your livestock. I add a calcium supplement almost daily and a buffer weekly or twice weekly, based on the test results I am seeing. I do not test daily, but a daily dose is most effective at creating the stability I want. I test Wednesdays and Sundays to confirm the dosing routine I am using is effective.
For the record, you will rarely see calcium remain high and alkalinity drop under the target range, both at the same time. When this occurs, you need a water change or small series of water changes, because the smaller buffering ions have been depleted. This should be a big warning sign to take quick action. As a general rule, personally, I rarely do water changes or any significant size unless this situation occurs.
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