{"id":124,"date":"2026-03-22T19:35:03","date_gmt":"2026-03-22T19:35:03","guid":{"rendered":"https:\/\/christoph-hoerth.de\/?page_id=124"},"modified":"2026-04-09T19:03:23","modified_gmt":"2026-04-09T19:03:23","slug":"nutrient-solution-fertilisation","status":"publish","type":"page","link":"https:\/\/christoph-hoerth.de\/?page_id=124","title":{"rendered":"Nutrient Solution & Fertilisation"},"content":{"rendered":"\n

Finding the Right Fertiliser<\/strong><\/p>\n\n\n\n

The nutrient solution in a recirculating living wall system presents a specific challenge: the fertiliser must be formulated for recirculating (non-drain-to-waste) hydroponics. In the German market, dedicated products for this application are scarce, and nothing is explicitly marketed for green walls. The category most likely to turn up in a search is cannabis cultivation products – a sector with well-developed recirculating hydroponic formulations, though the nutritional demands of cannabis as a heavy feeder cannot be directly translated to the shade-tolerant foliage plants typical of a living wall.<\/p>\n\n\n\n

\n\n\n\n

First Approach: Canna Aqua A&B \u2014 and Why It Failed<\/strong><\/p>\n\n\n\n

The initial fertiliser used was Canna Aqua A&B, which is specifically formulated for recirculating systems. In practice however a significant problem emerged: the pH of the solution dropped continuously over time, requiring manual correction with KOH every few days. Left unattended, the pH crashed to around 4, at which point several plants were lost.<\/p>\n\n\n\n

The underlying cause is plant physiology. Canna Aqua A&B is primarily ammonium-based. When a plant takes up ammonium (NH\u2084\u207a), it must maintain electrical charge balance across the root membrane. To compensate for the positive charge absorbed, the root excretes H\u207a ions into the surrounding solution – directly acidifying it. In a recirculating system with no drain-to-waste, this acidification accumulates rather than being flushed away. The effect is progressive and self-reinforcing: the more the plants grow and feed, the faster the pH falls.<\/p>\n\n\n\n

The practical consequence for a living wall is that ammonium-dominant fertilisers are poorly suited to closed recirculating systems unless active pH management is in place.<\/p>\n\n\n\n

\n\n\n\n

Current Approach: Advanced Nutrients Sensi Grow pH Perfect<\/strong><\/p>\n\n\n\n

The current fertiliser is Sensi Grow pH Perfect by Advanced Nutrients. The key distinction is that it is predominantly nitrate-based. When plants take up nitrate (NO\u2083\u207b), the charge balance mechanism works in reverse – the root releases OH\u207b or HCO\u2083\u207b to compensate, which has a mild alkalising effect that partially counteracts natural pH drift. The result is a much more stable pH over time without constant manual intervention.<\/p>\n\n\n\n

The “pH Perfect” claim from the manufacturer refers to a chelating technology that buffers pH within a target range \u2014 results in practice are better than with Canna Aqua, though the system still requires periodic monitoring.<\/p>\n\n\n\n

\n\n\n\n

Preparation Protocol<\/strong><\/p>\n\n\n\n

The following procedure has proven reliable in practice:<\/p>\n\n\n\n

    \n
  1. Base water:<\/strong> Fill the tank with tap water (local conductivity approximately 400 \u00b5S\/cm). The carbonate hardness in tap water provides a natural pH buffer – this is intentional and preferable to starting with RO water, which has no buffering capacity.<\/li>\n\n\n\n
  2. Add fertiliser:<\/strong> Dose Sensi Grow to reach a target conductivity of approximately 700 \u00b5S\/cm. Do not yet aim for the final target – phosphoric acid will contribute additional ions in the next step.<\/li>\n\n\n\n
  3. Adjust pH:<\/strong> Add phosphoric acid to bring pH to 6.0\u20136.5. This range ensures adequate availability of most macro- and micronutrients for the species used. Note that phosphoric acid is itself ionically active and raises conductivity measurably \u2014 typically by 100\u2013150 \u00b5S\/cm depending on the amount required. Phosphate is also a macronutrient, so this contribution is not merely incidental.<\/li>\n\n\n\n
  4. Measure final conductivity:<\/strong> After acid addition, measure conductivity again. This is the value that matters \u2014 it reflects the actual ion concentration the roots are exposed to. A final target of 800\u20131,000 \u00b5S\/cm has proven appropriate for the foliage species on this wall. If tip burn or marginal leaf scorch appears, reducing the target to 800 \u00b5S\/cm is worth considering.<\/li>\n\n\n\n
  5. Top-up:<\/strong> Top up weekly with reverse osmosis water (not tap water). As the plants transpire and the solution evaporates, volume decreases while dissolved salts remain \u2014 conductivity rises and pH shifts. Topping up with RO water dilutes back toward target. If top-up is skipped for too long, conductivity climbs, pH drops, and fertiliser burn becomes visible on older leaves.<\/li>\n\n\n\n
  6. Full tank refresh:<\/strong> Every 4\u20136 weeks, drain and prepare a fresh solution from scratch. This prevents accumulation of sodium, chloride, and unused nutrient ions that are not taken up by the plants.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    Finding the Right Fertiliser The nutrient solution in a recirculating living wall system presents a specific challenge: the fertiliser must be formulated for recirculating (non-drain-to-waste) hydroponics. In the German market, dedicated products for this application are scarce, and nothing is explicitly marketed for green walls. The category most likely to turn up in a search … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_kadence_starter_templates_imported_post":false,"footnotes":""},"class_list":["post-124","page","type-page","status-publish"],"_links":{"self":[{"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/pages\/124","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=124"}],"version-history":[{"count":4,"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/pages\/124\/revisions"}],"predecessor-version":[{"id":161,"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=\/wp\/v2\/pages\/124\/revisions\/161"}],"wp:attachment":[{"href":"https:\/\/christoph-hoerth.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=124"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}