Correct the pH of a prepared nutrient solution so plants can access nutrients within the appropriate range.

Choose HESI pH+ when the solution is too acidic or HESI pH− when it is too alkaline. Both are concentrated regulators intended for precise, incremental adjustment rather than use at a fixed dosage.

• Two directional options: pH+ raises pH, while pH− lowers it.
• Concentrated formulas: Only a small quantity is normally required to change the solution.
• Designed for nutrient solutions: Adjusts the final mixture after fertilisers and supplements have been added.
• Suitable throughout cultivation: Use whenever correction is required during vegetative growth or flowering.
• Useful for consistent reservoir management: Recording the amount used can provide a reference when preparing the same water and nutrient combination again.
• Transparent nutrient contribution: pH+ introduces potassium, while pH− introduces phosphorus.

Use as little regulator as necessary. Both variants alter the nutrient balance and can increase EC, so repeated correction in opposite directions should be avoided.

HESI pH regulators are primarily intended for:

• Hydroponic nutrient solutions
• Coco cultivation
• Semi-hydroponic and mineral-substrate systems
• Self-watering reservoirs
• Recirculating and non-recirculating irrigation systems
• Source water that remains outside the required range after nutrients are mixed

For many hydroponic and coco systems, HESI recommends a final pH of approximately 5.8 to 6.2. The correct target still depends on the plant, growing medium and cultivation system.

Routine pH correction is generally unnecessary for soil-based cultivation because soil buffers and modifies the root-zone pH differently. Measure the actual substrate conditions before using a concentrated regulator with soil-grown plants.

1. Add all base fertilisers and compatible supplements to the water.
2. Mix the nutrient solution thoroughly.
3. Measure the pH using a calibrated meter.
4. Select pH+ if the reading is too low or pH− if it is too high.
5. Add a very small amount of the selected regulator to the nutrient solution while mixing.
6. Wait 2 to 3 minutes for the solution to distribute and stabilise.
7. Measure again and repeat only if further correction is required.
8. Check the EC after adjustment because the regulator contributes additional dissolved minerals.

There is no universal dose. The amount required depends on the starting pH, water alkalinity, nutrient formula and solution volume. Do not assume that a particular number of drops always produces the same change.

Important safety precautions

• Wear chemical-resistant gloves and protective goggles.
• Work in a ventilated area and protect clothing and surrounding surfaces.
• Never mix concentrated pH+ and pH− directly together.
• Never combine either concentrate directly with undiluted fertiliser.
• Add the regulator to the prepared solution, not water or fertiliser to the regulator bottle.
• Use separate, clean dosing tools for pH+ and pH−.
• Keep the bottles upright, tightly closed and in their original packaging.
• Keep away from children and animals.

Both products are corrosive and can cause severe skin burns and eye damage. In case of contact, immediately rinse with plenty of water, remove contaminated clothing and follow the instructions on the product label. Obtain urgent medical advice for eye exposure, ingestion or significant skin contact.

HESI provides two concentrated pH regulators:

• HESI pH+: 50% potassium hydroxide solution for raising the pH of prepared nutrient solutions.
• HESI pH−: 59% phosphoric acid solution for lowering the pH of prepared nutrient solutions.

Available options

• pH+: 1 × 1 L bottle of HESI pH+.
• pH−: 1 × 1 L bottle of HESI pH−.
• Combo: 1 × 1 L bottle of HESI pH+ and 1 × 1 L bottle of HESI pH−.

pH+ contributes potassium to the nutrient solution, while pH− contributes phosphorus. Both formulas are highly concentrated and corrosive. Always follow the safety instructions on the original packaging and use only the amount required to reach the target pH.