{"id":45869,"date":"2026-10-22T03:09:06","date_gmt":"2026-10-22T00:09:06","guid":{"rendered":"https:\/\/mytankscape.com\/?p=45869"},"modified":"2026-10-22T03:09:06","modified_gmt":"2026-10-22T00:09:06","slug":"reef-water-chemistry-alkalinity-calcium-magnesium-guide","status":"publish","type":"post","link":"https:\/\/mytankscape.com\/en\/reef-water-chemistry-alkalinity-calcium-magnesium-guide\/","title":{"rendered":"Reef Water Chemistry Explained: Alkalinity, Calcium and Magnesium"},"content":{"rendered":"<div class=\"mts-article\">\nMost reef problems that look like a coral problem are really a chemistry problem. Learn three numbers and how they move together, and you can stop guessing why a coral is pale, slow or losing tissue.<\/p>\n<div class=\"mts-summary\">\n<strong>Quick answer:<\/strong> Reef corals that build a stony skeleton need steady <strong>alkalinity (about 8\u201311 dKH), calcium (about 400\u2013450 ppm) and magnesium (about 1,250\u20131,350 ppm)<\/strong> at a salinity of roughly 1.025 and a temperature of 24\u201326\u00b0C. Alkalinity is the one that matters most and moves fastest, so test it first and most often. <strong>A steady number beats a perfect number<\/strong>: avoid swings of more than about 1 dKH in a day, change one thing at a time, and retest before you dose again.\n<\/div>\n<h2 id=\"toc\">Table of Contents<\/h2>\n<ul class=\"mts-checklist\">\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#why\">Why Chemistry Matters on a Reef<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#big3\">The Big Three: Alkalinity, Calcium, Magnesium<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#others\">The Supporting Numbers<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#table\">Target Ranges at a Glance<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#testing\">How and When to Test<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#replace\">Replacing What Corals Use Up<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#dosing\">Dosing Safely<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#trouble\">Troubleshooting by Symptom<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#heat\">Cairo Summers and Chemistry<\/a><\/li>\n<li><a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"#faq\">FAQ<\/a><\/li>\n<\/ul>\n<h1>Reef Water Chemistry Explained: Alkalinity, Calcium and Magnesium<\/h1>\n<h2 id=\"why\">Why Chemistry Matters on a Reef<\/h2>\n<p>Stony corals, which include LPS and SPS types, build their skeletons from calcium carbonate. To do that they pull <strong>calcium<\/strong> and <strong>carbonate alkalinity<\/strong> out of the water, and they need <strong>magnesium<\/strong> to keep those two dissolved instead of crashing out as crust. Soft corals such as zoanthids do not build a heavy skeleton, so they use far less, which is one reason they are easier for beginners.<\/p>\n<p>The key idea is that a reef tank is a closed box. Whatever the corals consume does not come back on its own, and that is why numbers drift downward over days. Your job is to measure the drift and replace what was used, gently and steadily. If you have not set up your tank yet, start with our <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/saltwater-reef-tank-setup-guide\/\">reef setup guide<\/a>.<\/p>\n<h2 id=\"big3\">The Big Three: Alkalinity, Calcium, Magnesium<\/h2>\n<h3>Alkalinity (KH) \u2013 The Number That Matters Most<\/h3>\n<p>Alkalinity measures the water&#8217;s carbonate &#8220;buffer.&#8221; It is the raw material for coral skeletons and it also keeps pH from swinging. A target of <strong>about 8\u201311 dKH<\/strong> suits most reefs, and many beginners do well holding steady near the lower-middle of that range. Alkalinity is consumed fastest and changes fastest, so a stable alkalinity matters more than hitting a high one.<\/p>\n<p>You will see three units. As a conversion, <strong>1 meq\/L equals about 2.8 dKH<\/strong>, and <strong>1 dKH equals about 17.9 ppm<\/strong>. Check which unit your test kit reports so you compare like with like.<\/p>\n<div class=\"mts-warning\">\n<strong>Warning:<\/strong> Rapid alkalinity swings stress and can kill stony corals. As a common rule of thumb, avoid changing alkalinity by more than about 1 dKH in a day, up or down.\n<\/div>\n<h3>Calcium \u2013 The Building Block<\/h3>\n<p>Natural seawater holds roughly 410\u2013420 ppm of calcium at a salinity of 35 ppt, and a reef target of <strong>about 400\u2013450 ppm<\/strong> suits most tanks. Calcium usually moves more slowly than alkalinity, because the tank holds a lot of it compared with what corals take each day.<\/p>\n<h3>Magnesium \u2013 The Quiet Referee<\/h3>\n<p>Magnesium keeps calcium and alkalinity from precipitating out of the water as cloudy crust. A target of <strong>about 1,250\u20131,350 ppm<\/strong> is typical. If magnesium runs low, you will find calcium and alkalinity hard to hold in range, no matter how much you dose. Test it every so often and correct it before chasing the other two.<\/p>\n<h3>How the Three Move Together<\/h3>\n<p>When a stony coral grows, it consumes calcium and alkalinity together, in a fixed ratio. In practice, dropping alkalinity by <strong>1 dKH<\/strong> goes with using up roughly <strong>7 ppm of calcium<\/strong>. Because seawater holds so much calcium and relatively little alkalinity, alkalinity is the one that runs out first. That is why most reef keepers watch alkalinity most closely and calcium less often.<\/p>\n<div class=\"mts-product-callout\">\n<strong>Which of your corals use the most?<\/strong> Soft corals such as the <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/zoanthid-coral-live\/\">Zoanthid Coral<\/a> draw down very little. Stony LPS corals such as the <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/acan-brain-coral\/\">Acan Brain Coral<\/a> and <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/lobophyllia-coral-live-lps-coral\/\">Lobophyllia Coral<\/a> use moderate amounts, and fast-growing SPS use the most. Add stony corals one at a time so you can see the effect on your numbers.\n<\/div>\n<h2 id=\"others\">The Supporting Numbers<\/h2>\n<ul class=\"mts-checklist\">\n<li><strong>Salinity:<\/strong> keep it near 1.025 specific gravity (about 35 ppt), measured with a refractometer. Calcium, magnesium and alkalinity all scale with salinity, so a drifting salinity makes every other reading drift too.<\/li>\n<li><strong>Temperature:<\/strong> 24\u201326\u00b0C, steady. Warm water holds less oxygen and stresses corals long before it kills them.<\/li>\n<li><strong>pH:<\/strong> roughly 8.0\u20138.4, with a small daily rise and fall. A pH that sits very low usually points to low alkalinity or poor gas exchange.<\/li>\n<li><strong>Nitrate:<\/strong> low but not zero, roughly 2\u201310 ppm. High nitrate feeds algae; zero can leave corals pale.<\/li>\n<li><strong>Phosphate:<\/strong> low but not zero, roughly 0.01\u20130.08 ppm. Too much fuels algae that can smother coral.<\/li>\n<\/ul>\n<p>The simple &#8220;ammonia, nitrite and nitrate&#8221; tests in our <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/water-parameters-101-testing-ph-ammonia-nitrite-nitrate\/\">Water Parameters 101<\/a> guide still apply to a reef. The reef-specific numbers are the extra layer on top.<\/p>\n<h2 id=\"table\">Target Ranges at a Glance<\/h2>\n<p>Hobby sources differ slightly, so treat these as ranges, not exact lines. What matters is that the readings stay steady from day to day.<\/p>\n<div style=\"overflow-x:auto;\">\n<table style=\"border-collapse:collapse;width:100%;min-width:560px;\">\n<thead>\n<tr>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">Parameter<\/th>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">Target<\/th>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">What it does<\/th>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">If it drifts<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Alkalinity<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">8\u201311 dKH<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Skeleton material, pH buffer<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Slow growth, tissue loss, pH swings<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Calcium<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">400\u2013450 ppm<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Skeleton building block<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Stunted stony coral growth<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Magnesium<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">1,250\u20131,350 ppm<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Keeps Ca and alkalinity dissolved<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Cloudy water, hard to hold Ca and alk<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Salinity<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">1.025 (35 ppt)<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Base for every other value<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Osmotic stress, all readings shift<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Nitrate<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">About 2\u201310 ppm<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Nutrient for algae and zooxanthellae<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">High: algae. Zero: pale corals<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Phosphate<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">About 0.01\u20130.08 ppm<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Nutrient, also affects skeleton growth<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">High: algae. Very low: stalled growth<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 id=\"testing\">How and When to Test<\/h2>\n<ul class=\"mts-checklist\">\n<li><strong>New tank, soft corals only:<\/strong> test alkalinity, calcium, magnesium, salinity and nitrate weekly.<\/li>\n<li><strong>After adding a stony coral:<\/strong> test alkalinity daily for the first week so you see how fast the tank uses it.<\/li>\n<li><strong>Established stony-coral tank:<\/strong> test alkalinity every few days, and calcium and magnesium weekly.<\/li>\n<li><strong>Test at the same time of day,<\/strong> because alkalinity and pH shift slightly through the lighting cycle.<\/li>\n<li><strong>Write every result down.<\/strong> The trend tells you more than any single reading, and a log makes a slow downward drift obvious before corals show it.<\/li>\n<li><strong>Use fresh reagents and follow the instructions exactly,<\/strong> including the sample volume and timing. Old or sloppy tests are the most common reason for &#8220;mystery&#8221; readings.<\/li>\n<li><strong>Double-check surprising results<\/strong> by testing again, or with a second kit, before you react.<\/li>\n<\/ul>\n<div class=\"mts-tip\">\n<strong>Tip:<\/strong> If you do not want to run tests yourself yet, our <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/marine-reef-aquarium-maintenance-plans\/\">Marine &amp; Reef Aquarium Maintenance<\/a> visits include the test reagents. Marine Pro adds KH and phosphate checks, and Reef Prime tests KH, phosphate, calcium and magnesium and keeps a log.\n<\/div>\n<h2 id=\"replace\">Replacing What Corals Use Up<\/h2>\n<p>There are three levels of reef chemistry management, and most keepers move up as their coral collection grows.<\/p>\n<ol>\n<li><strong>Water changes only:<\/strong> a regular change with fresh, properly mixed saltwater replenishes calcium, magnesium and alkalinity together. For a tank with mostly soft corals or a few small LPS, this is often enough. Our <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/how-often-should-you-change-aquarium-water-complete-guide\/\">water change guide<\/a> covers the routine.<\/li>\n<li><strong>Supplements:<\/strong> when stony corals use more than water changes replace, you add calcium and alkalinity separately, using a &#8220;two-part&#8221; solution or an all-in-one supplement, following the product&#8217;s directions.<\/li>\n<li><strong>Automation:<\/strong> larger or SPS-heavy tanks often move to automatic dosing pumps, a calcium reactor, or kalkwasser (limewater) added through the top-off water, so supply tracks consumption without daily manual work.<\/li>\n<\/ol>\n<p>Whatever you choose, <strong>the supplement should match measured consumption<\/strong>, not a calendar. Dosing a fixed amount &#8220;just in case&#8221; is how numbers climb out of range.<\/p>\n<h2 id=\"dosing\">Dosing Safely<\/h2>\n<ul class=\"mts-checklist\">\n<li><strong>Test first, then dose.<\/strong> Never add a supplement without a fresh reading.<\/li>\n<li><strong>Change one parameter at a time.<\/strong> Adjust alkalinity or calcium, retest, then move on.<\/li>\n<li><strong>Small steps:<\/strong> raise alkalinity by well under 1 dKH per day, and spread larger corrections over several days.<\/li>\n<li><strong>Add solutions slowly,<\/strong> into a high-flow area such as near a pump outlet, so they mix at once rather than forming a cloud.<\/li>\n<li><strong>Keep calcium and alkalinity doses apart<\/strong> in time and place. Dosed together in a still spot they can precipitate, leaving cloudy water and lower readings than you expected.<\/li>\n<li><strong>Fix magnesium first<\/strong> if it is low, because low magnesium makes the other two hard to hold.<\/li>\n<li><strong>Follow the product label,<\/strong> and remember that &#8220;more&#8221; is never the answer in a closed system.<\/li>\n<\/ul>\n<p>Flow matters here too. Strong, even circulation mixes anything you add and carries nutrients to every coral, which is why a wave maker is a core piece of reef equipment.<\/p>\n<div class=\"mts-product-callout\">\n<strong>Equipment that supports stable chemistry:<\/strong> the <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/jebao-rw4-wave-maker-pump-700-8000lh\/\">Jebao RW-4 Wave Maker Pump<\/a> mixes dosed solutions quickly and keeps flow even, and the <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/bubble-magus-curve-5-protein-skimmer-up-to-500l\/\">Bubble Magus Curve 5 Protein Skimmer<\/a> removes dissolved waste before it turns into nitrate and phosphate.\n<\/div>\n<h2 id=\"trouble\">Troubleshooting by Symptom<\/h2>\n<div style=\"overflow-x:auto;\">\n<table style=\"border-collapse:collapse;width:100%;min-width:520px;\">\n<thead>\n<tr>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">What you see<\/th>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">Likely chemistry cause<\/th>\n<th style=\"border:1px solid #cbd5e1;padding:8px;text-align:start;\">First step<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Stony coral losing tissue<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Alkalinity swing or a drop<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Test alkalinity now and stop any large corrections<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Slow or stalled growth<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Low alkalinity, calcium or magnesium<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Test all three and fix magnesium first if low<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Cloudy white water after dosing<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Precipitation from dosing too fast or too close together<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Pause dosing, increase flow, retest in a day<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Pale or bleached coral<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Heat, too much light, or nutrients that are too low<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Check temperature, then nitrate and phosphate<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Algae outbreak<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">High nitrate or phosphate<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Test both, water change, check skimmer and feeding<\/td>\n<\/tr>\n<tr>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Every reading keeps drifting<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Salinity is moving, often from evaporation<\/td>\n<td style=\"border:1px solid #cbd5e1;padding:8px;\">Check salinity and top off with fresh RO\/DI water<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h2 id=\"heat\">Cairo Summers and Chemistry<\/h2>\n<p>Hot weather affects chemistry in two ways. First, evaporation speeds up, which pushes salinity and every dissolved value upward if you do not top off with fresh RO\/DI water. Second, warmer water holds less oxygen and puts corals under stress, so a small chemistry slip hurts more. Keep the tank cool, top off daily, and read <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/how-to-cool-your-aquarium-in-summer-heat\/\">How to Cool Your Aquarium in Summer Heat<\/a> before the first heatwave. Evaporative fans work, but they raise evaporation further, so check salinity more often when you use them.<\/p>\n<div class=\"mts-product-callout\">\n<strong>Summer cooling:<\/strong> the <a class=\"mts-link\" style=\"color:#1a56db;text-decoration:underline;font-weight:600;font-size:1.03em;\" href=\"https:\/\/mytankscape.com\/en\/shop\/aquarium-cooling-fan-set\/\">Aquarium Cooling Fan Set<\/a> comes with 1 to 4 fans and an optional temperature sensor for automatic control. If you want ready-made water for a change, the maintenance plan page notes that RO water, marine salt or ready-mixed saltwater can be bought from us at a separate cost.\n<\/div>\n<h2 id=\"faq\">Frequently Asked Questions<\/h2>\n<div class=\"mts-faq\">\n<strong>What is the most important reef parameter?<\/strong><br \/>Alkalinity. It is consumed fastest, it drives pH stability, and sudden swings are the most common chemistry cause of stony coral problems.\n<\/div>\n<div class=\"mts-faq\">\n<strong>What should my alkalinity be?<\/strong><br \/>Roughly 8\u201311 dKH for most reefs. Choose a value in that range and hold it steady rather than chasing the top of it.\n<\/div>\n<div class=\"mts-faq\">\n<strong>How often should I test reef water?<\/strong><br \/>Weekly for a soft-coral tank, every few days for alkalinity in a stony-coral tank, and daily for the first week after adding a new stony coral.\n<\/div>\n<div class=\"mts-faq\">\n<strong>Do soft corals need calcium and alkalinity dosing?<\/strong><br \/>Usually very little. A tank with mostly soft corals is often maintained with regular water changes and weekly testing.\n<\/div>\n<div class=\"mts-faq\">\n<strong>Why does my water go cloudy when I dose?<\/strong><br \/>Calcium and alkalinity supplements can precipitate if added too fast or in the same spot. Slow down, add them in a high-flow area, and separate the doses.\n<\/div>\n<div class=\"mts-faq\">\n<strong>What is the difference between dKH, meq\/L and ppm?<\/strong><br \/>They are different units for alkalinity. As a conversion, 1 meq\/L equals about 2.8 dKH, and 1 dKH equals about 17.9 ppm.\n<\/div>\n<div class=\"mts-faq\">\n<strong>Can I fix chemistry quickly with a big water change?<\/strong><br \/>A large change can shock corals if the new water differs from the tank. Make corrections gradually, and match salinity and temperature when you change water.\n<\/div>\n<h2>Conclusion<\/h2>\n<p>Three numbers, one habit. Keep alkalinity, calcium and magnesium in range and steady, test on a schedule, log the results, and dose only what you have measured. 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Learn three numbers and how they<\/p>\n","protected":false},"author":298,"featured_media":45870,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"wpai_generated_summary":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"mts_hero_image_prompt":"","mts_hero_image_alt":"","_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[1215],"tags":[1237,1243,1213,1239,1195,1241,1197,1235,1209,998],"class_list":["post-45869","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-reef-marine","tag-alkalinity","tag-aquarium-dosing","tag-beginner-reef-keeping","tag-calcium","tag-coral-care","tag-magnesium","tag-reef-aquarium","tag-reef-water-chemistry","tag-saltwater-aquarium","tag-water-testing"],"jetpack_sharing_enabled":true,"jetpack_likes_enabled":false,"jetpack-related-posts":[],"jetpack_featured_media_url":"https:\/\/mytankscape.com\/wp-content\/uploads\/2026\/10\/reef-water-chemistry-alkalinity-calcium-magnesium-hero.png","_links":{"self":[{"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/posts\/45869","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/users\/298"}],"replies":[{"embeddable":true,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/comments?post=45869"}],"version-history":[{"count":1,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/posts\/45869\/revisions"}],"predecessor-version":[{"id":45873,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/posts\/45869\/revisions\/45873"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/media\/45870"}],"wp:attachment":[{"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/media?parent=45869"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/categories?post=45869"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mytankscape.com\/en\/wp-json\/wp\/v2\/tags?post=45869"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}