How often should I calibrate GT pH Up & pH Down?

pH meters should be calibrated before every use or at minimum every 2–3 days during active grows. EC meters are more stable but should be verified against a known reference solution weekly. GT pH Up & pH Down uses two-point calibration for pH (4.0 and 7.0 buffer solutions) and single-point calibration for EC (2.77 mS/cm standard). Regular calibration is the single most important factor in measurement accuracy.

How do I store GT pH Up & pH Down properly?

Always store pH probes wet — never allow the probe tip to dry out as this permanently damages the glass membrane. Use the probe storage solution supplied with GT pH Up & pH Down or Bluelab KCl storage solution. EC probes are more robust but should also be rinsed with clean water after each use. Store GT pH Up & pH Down at room temperature away from direct sunlight.

What should I do if GT pH Up & pH Down is reading incorrectly?

First, recalibrate using fresh buffer solutions — old or contaminated calibration fluid is the most common cause of inaccurate readings. Rinse the probe thoroughly with deionised or distilled water between calibrations. If readings are still inconsistent after recalibration, check the probe for physical damage or contamination. Most probes have a service life of 12–18 months with proper care.

Is GT pH Up & pH Down waterproof?

Check the IP rating listed in the product specifications. Most handheld meters are splash-proof but not designed for submersion. Take care when measuring in deep reservoirs to avoid dropping the unit. GT pH Up & pH Down is designed for hydroponic nutrient solution testing — it is not rated for outdoor or continuous immersion use.

Does GT pH Up & pH Down ship fast within Australia?

Yes — GT pH Up & pH Down ships from our Australian warehouse with fast tracked delivery Australia-wide. Most east coast orders arrive within 2–5 business days. WA, NT, and TAS orders typically arrive within 5–12 business days.

GT pH Up & pH Down | Precision pH Control for Maximum Nutrient Uptake

GT pH Down concentrate 250ml

$14.95

GT pH Up & pH Down | Precision pH Control for Maximum Nutrient Uptake

$14.95

Type and Size GT pH Down concentrate 250ml GT pH Up concentrate 250ml GT pH Down 1L GT pH Up concentrate 1L

Quick Answer

Precision pH control system, potassium hydroxide (Up) and phosphoric acid (Down).
Keeps nutrients within the 5.5 to 6.5 optimal availability range, where deficiencies stop appearing.
Best suited to any grower wanting fast, accurate pH correction regardless of growing method.
Always adjust pH last, after nutrients and additives are already in the water.

GT pH Up & pH Down is a precision pH control system for hydroponic and soil growers who want their nutrients to actually work. pH is the single variable that determines whether the nutrients you're feeding are available to your plants, drift outside the 5.5 to 6.5 optimal range and deficiencies appear regardless of what's in your reservoir.

GT pH Up (potassium hydroxide) and pH Down (phosphoric acid) give you fast, accurate control over your nutrient solution, with the added benefit of contributing potassium and phosphorus as secondary nutrients. Compatible with hydroponics, coco coir, and soil.

Key Benefits

Maintains the 5.5 to 6.5 pH range where nutrient uptake is most efficient
Prevents nutrient lockout caused by pH drift in recirculating systems
pH Up (KOH) adds potassium as a beneficial secondary nutrient
pH Down (H₃PO₄) adds phosphorus and is stable across most nutrient programs
Professional-grade concentrations for precise, predictable adjustments

How It Works

pH controls whether your nutrients are available to your plants. When it drifts, even a well-mixed solution stops working. pH Up raises pH to bring an acidic solution back into range. pH Down lowers it when your water or nutrients push things too alkaline. In recirculating systems, pH shifts naturally over time as plants feed, so checking and adjusting regularly isn't extra work, it's just part of running a dialled-in system.

How to Use

Always adjust pH after adding nutrients and additives to your solution. Add small amounts gradually, mix thoroughly, and re-test before adjusting further. Monitor daily in recirculating systems. Allow solution to stabilise 30 to 60 minutes before making a final pH reading for accuracy.

Small, frequent adjustments are more accurate than large corrections, overshoot in either direction and you'll be chasing pH all day.

⚠️ Safety & Handling

pH Up (Potassium Hydroxide): Highly alkaline and caustic. Always wear gloves and eye protection. Dilute before adding to tank. Store securely away from children. Safety Data Sheets available on request.

pH Down (Phosphoric Acid 85%): Highly corrosive. Always wear gloves and eye protection. If skin or eye contact occurs, wash immediately with water. Dilute before adding to tank. Store securely away from children. Safety Data Sheets available on request.

pH control is one of the highest ROI adjustments in any grow system. Get it right and everything else in your feed program performs better.

Frequently Asked Questions

How much pH Down do I need to add?

Far less than most people expect. Phosphoric acid at 85% is strong, so start with a fraction of a millilitre per litre, mix thoroughly, and re-test before adding more. Overshooting means chasing pH back the other way and building up salts in the process.

Do I adjust pH before or after adding nutrients?

After, always. Base nutrients and additives shift pH themselves, sometimes significantly. Adjusting first and then adding feed means starting again. Mix everything in, let it settle, then correct.

Why does my pH keep drifting back up?

In recirculating systems pH rises naturally as plants take up nutrients and as the solution ages. A slow climb over days is normal. A rapid swing usually points at something else, an undersized reservoir, root problems, or a solution that needs changing rather than correcting.

Can I use pH Up and pH Down in soil as well as hydroponics?

Yes. Soil buffers pH more than an inert medium does, so you will generally need less adjustment and it will hold longer. Adjust the water going in rather than trying to correct the soil itself.

Is pH Up or pH Down dangerous to handle?

Both need respect. pH Up is caustic potassium hydroxide, pH Down is 85% phosphoric acid. Gloves and eye protection every time, dilute before adding to the tank, and never store them where children can reach. Safety Data Sheets are available on request.

What pH should I actually be running?

5.5 to 6.5 covers most hydroponic growing, with 5.8 to 6.2 the range most growers settle on. Slightly different crops prefer slightly different points within that band, but staying inside it matters more than hitting an exact number.