How important is it to have stable alkalinity for a reef tank? It’s VERY important. In fact, on my list of Top 10 Tips For Keeping a SPS Reef Tank  I have stable parameters, especially alkalinity, at #1.


Yes, a sudden change in alkalinity can be very detrimental to sensitive SPS corals so it is best to monitor this parameter on a daily basis. For years I had been using a hobby grade test kit from Salifert to track alkalinity but I was only doing so on a weekly basis. The Salifert test kit is very easy to use but it is not economical to test each day. And, call me lazy, who wants to manually test alkalinity EACH day?

Necessity is The Mother of Invention

They say “necessity is the mother of invention” and a few years ago a number of companies rolled out alkalinity monitors, giving hobbyists the means to constantly monitor alkalinity on an automated basis.

These monitors are a bit pricey but they don’t cost a lot to maintain. I use the KH Director from GHL and over the eight months I have used the unit I spent only $60 for a couple of bottles of reagent. Nonetheless, I believe the cost of entry to own one of these lab grade units is absolutely worth it.


I only monitor alkalinity once per day but you can test multiple times a day. Below is a daily track of my tank’s alkalinity during the first month I began using the KH Director. As you can see, there were minimal variations by day, a good thing, as noted above, for SPS health.


alkalinity monitoring


But there is more to this chart than meets the eye. In a broader sense, it can provide important insights into whether a tank’s corals are consuming the right amount of calcium and alkalinity. A key indicator of their health.

What to Look For

A slow downward trend in alkalinity is good as it suggests corals are sucking up what they need. If levels are not dropping then either too much is being supplemented or the corals are not happy due to another issue (e.g. lack of trace elements, very low nitrates or phosphates, etc.). When I see slow declines I eventually bump up dosing to keep my alkalinity within a desired range, which yields a series of slight ups and downs over time.


Overall, the more data points you have the easier it will be to spot trends and course correct, food for thought for those on the fence about purchasing an alkalinity monitor. Oh, did I mention these monitors provide lab grade results versus hobbyist test kits? More food for thought 🙂



So that’s the skinny. One very important note to disclose, I do sell KH Directors but I only sell or recommend products I use personally and believe will be good for my readers. If you would like more information or would like to purchase a KHD please visit the Equipment section on


Shop KH Directors Now



If you are looking for additional insights and information, please explore my many other reef tank and SPS related articles as well as my book, A ReefBum’s Guide To Keeping an SPS Reef Tank: A Blueprint For Success. Additionally, you can see all of my reef tank videos online now as well as my Live HD Webcam. And if you are interested in purchasing affordable SPS frags that are pest-free and homegrown, you can visit my SPS Frag store.


Happy reef keeping!

**Disclosure of Material Connection**
This is a “sponsored post.” The company who sponsored it compensated me via a cash payment, gift, or something else of value to produce it. Regardless, I only recommend products or services I use personally and believe will be good for my readers. I am disclosing this in accordance with the Federal Trade Commission’s 16 CFR, Part 255: “Guides Concerning the Use of Endorsements and Testimonials in Advertising.”