Water Quality & pH for Rare Aroids — Why Tap Water Is a Problem

Israeli tap water is 'safe' for drinking — for humans. For plants, it is the slow poison. Look at the pH of your tap water. It is typically between 7.0–8.5 in Israel — neutral to alkaline. Epiphytic plants like *Monstera*, *Philodendron*, and *Alocasia* evolved in acidic environments: leaf litter, natural soil — everything that keeps pH down to 5.5–6.5. At this acidity, they can absorb minerals (Ca, Mg, K, N) at good rates. At pH 7.5+, these plants start to suffer from deficiencies — not because minerals are absent, but because the plant cannot absorb them when the media is too alkaline. Solute content (TDS/EC) is the second issue. Tap water in Israel often carries 300–600 ppm (Total Dissolved Solids). For a TC plant fresh from the flask, 300ppm is already stressful. The higher the TDS, the greater the osmotic gradient — water is pulled out of plant cells to balance the external salt concentration. The result: leaves lose turgor, edges yellow and brown, roots weaken. If you are using tap water for months, salts accumulate in the substrate and never wash out. RO water (Reverse Osmosis) is near-perfect: TDS close to zero, pH 6.8–7.0 (neutral, but low enough to work with). However, it is not common in Israel and usually requires home investment. Distilled water is similar to RO: very low TDS (nearly zero), pH slightly acidic (5.5–6.0 due to dissolved CO₂ from air). Better than tap, much cheaper than RO (can buy at any supermarket). Filtered water (Brita, etc.) reduces chlorine and some minerals, but TDS may still be 150–250ppm — not ideal, but far better than tap. The ideal is: TDS 50–150ppm, pH 6.0–6.5. How to achieve this: start with RO or distilled (TDS near zero), add a micro-dose of balanced fertilizer to reach EC 0.4–0.6, adjust pH to 6.0–6.5 with pH Down (phosphoric acid) if needed. This mimics rainwater — which is what aroids 'expect' in nature. For daily watering: use distilled or RO. For monthly nutrient watering (in LECA setups), add EC 0.6–0.8 solution. For regular pot-soil plants: alternate distilled weeks with low-dose nutrient weeks. Do not skip pH measurement. A digital pH meter costs 20–30 sheqel. Your rare Monstera costs 2,000. The investment is obvious.