pH Correction
It is most important to maintain the correct pH of a nutrient solution.
pH is often regarded as the key which unlocks the doors to the various elements in a nutrient solution and makes them available to a plant.
If a hydroponic system is not operated at the correct pH level then many elements will be unavailable to a plant in the correct proportions and deficiencies can become apparent.
Pure Hydroponics recommends a nutrient solution pH range of between 5pH – 6.2pH for all crop types.
5.8 pH is the optimum level as it is low enough to keep the root zone of the plant consistently below 6.2pH and high enough to reduce the risk of overdosing the acid.
Healthy, feeding plants should naturally raise the pH of the nutrient solution or growing media as they consume nutrients.
It is therefore not necessary to use a pH Raise solution, the plants will raise the pH themselves.
All that is required is to add a weak hydroponic acid to lower the pH of the nutrient solution and keep it within the acceptable 5 – 6.2pH range.
All concentrated acids should be diluted to between 5 & 10% strength before being added to a hydroponic mixing tank.
Concentrated acid does not mix well when added to a nutrient solution tank. There is the risk that it can sink to the bottom of the tank as a concentrated glob and cause root system damage if it is sucked up by the pump and fed to the crop.
Concentrated acid can also cause a localised reaction with nutrients in the tank if it is added too strongly. Always make a dilute 5 – 10% pH stock solution to draw from.
“Little and Often” is always the best rule to follow when adding acid to a hydroponic tank. This allows for a gradual lowering of the pH rather than drastic changes which can easily fall beyond the minimum pH range.
If for any reason you add too much acid and the pH drops too quickly, then turn off the pump and purge some of the tank solution and add fresh water (which is closer to 7pH) to raise the pH again.
Always add acid to water. Never add water to concentrated acid or it will boil and splash and cause injury.
Safety goggles and gloves are compulsory when using concentrated acid. You don’t get any second chances if a concentrated acid splashes in the eyes.
Drum Pumps with a Safety Measure device are ideal for decanting concentrated acids (as listed in the products section on this website).
Pure Hydroponic recommends the following acids for lowering the pH of a nutrient solution:
Nitric Acid – Nitric Acid should be used by itself for growing over the summer months.
Phosphoric Acid – A small amount of Phosphoric Acid should be added to the Nitric Acid over Winter at a ratio of 1 part Phosphoric Acid to 6 parts Nitric Acid. This transition should occur when night time temperatures become cooler as Winter approaches (usually after late March or early May in the Southern Hemisphere). Return to using Nitric Acid by itself as the nights get warmer.
Nitric or Phosphoric Acid is available in the following grades:
- 500ml (Diluted acid for small domestic systems)
- 2 Litre (Diluted acid for small domestic systems)
- 20 Litre (Full strength acid for commercial systems)
- 200 Litre (Full strength acid for commercial systems)
pH Raise solution (Caustic Potash) is also available for clients with special circumstances.
For pH Testing we recommend the Bluelab pH Pen, Bluelab pH Meter or the Bluelab Combo Meter (as showcased on this website).
Please talk to Pure Hydroponics for pricing and shipping.
Further information on pH management for hydroponic crops can be found in the article below:
pH Management of Hydroponic Solutions
