pH Up is a strong alkali formula for raising pH. The one from General Hydroponics is made from a base of Potassium Hydroxide and Potassium Carbonate.
pH Down is an acid based formula for lowering pH. General Hydroponics up/down is made from a base of Phosphoric Acid.
As explained above, adjust the pH of your solution a little at a time. Try to use only either Up or Down. If you overshoot with one and then have to readjust with the other you can end up unnecessarily stressing your plants. Mix up a little of the required pH adjuster in a separate jug. Then add them a little at a time to your reservoir. Allow time for the whole reservoir to even out and settle. Better to get it right with 3 slight adjustments than have it wildly swinging up and down.
Due to the constant availability of nutrients in a solvent form in hydroponics there is a greater range of tolerance in pH fluctuation. Cannabis grows well hydroponically within a range of 5.5-6.5. Usually the pH is regulated to 5.8-6.0 for hydroponic systems with a growing medium that has been stabilized.
Add the required nutrients to your water until you have the appropriate EC (nutrient concentration) for your plants.
Measure the pH of the nutrient solution.
If the pH is still too high add vinegar * or pH DOWN until the solution has the correct pH.
If the pH is too low add pH UP until the solution has the correct pH.
When you are using tap water let it sit in a container for a few hours so that the chlorine evaporates.
*Vinegar is a neutral acid that is completely harmless to plants when diluted in water. It can be used for Hydrofarms with hydro correls and on rockwool. Not all growing mediums may be suitable. run a test if you are using coco coir or other substrates.
Fertilizing a plant that is suffering from a pH imbalance usually increases the cycle of problems. It may show a brief respite to symptoms, but only because the fertilizer added to the water may have changed the pH favourably for a short time. Without paying attention to the actual problem and adjusting the pH to the correct range your plants will continue to suffer and you will lose yield on a daily basis.
All of these factors influence how the pH should be adjusted and how it changes in the containers or tank over a period of time. A fluctuation of one full point in hydroponics can usually be tolerated by cannabis as long as the pH is stabilized to the ideal range within 24 hrs. For best results the pH should therefore be monitored daily in a system with large fluctuation.
The pH is the measure of the acidity or alkalinity of a solution or substrate. A low pH shows that the solution is acidic and a high pH that it is base/alkaline. The middle value of approx. pH 6.8 is the neutral range. The pH is absolutely vital for all living organisms in various ways.