Checking the pH in your hydroponic solution is a key element of successful gardening! Most plants do well in a slightly acidic solution, so try to maintain an average pH of 6.3. If your pH is too high (alkaline), add pH DOWN to lower the pH. If pH is too low (acidic), add pH UP to adjust the water. Check pH—and adjust if necessary—every 1-2 days! (All products on this page are for checking and adjusting pH of water or nutrient solutions. Click here for Soil pH Testers).

pH Meters & Testers

pH Test Kit

Tests the pH of water or nutrient solution--add 3 drops of test fluid to water sample, then compare to a color chart. Each kit yields about 100 tests.

• pH Test Kit, $6.99

Litmus Paper

Litmus paper test just like you used in science class! Tear off a 2" strip then dip into nutrient solution. A vivid color change indicates pH.

• Litmus Paper, 5.5 to 8.0 range, $8.99
• Litmus Paper, 0-13 range, $8.99

Control Wizard pH-1 Pen

This pen is an inexpensive and effective way to test your pH with digital accuracy. Range is from 1 to 14. Includes protective case and comes with a 1 year warranty.

• Control Wizard pH-1 Pen, $38.99

Oakton Waterproof Digital pH Pen

Battery-powered test pen displays digital reading of a liquid's pH, expressed in 0.1 increments from 0 to 14. Waterproof. Includes protective case and replaceable electrode. 2-year warranty (1-year on probe).

• Oakton Waterproof Digital pH Pen, $84.99

NutraDip Constant pH Monitor

Just place the remote electrode into your nutrient reservoir, then turn on the monitor for an instant--and constant--pH display. The sealed casing keeps moisture out, and the electrode is replaceable. Warranty 6 months electrode, 2 years monitor.

• NutraDip Constant pH Monitor (AC powered), $136.99

pH Adjusters

pH Down

A 9% Phosphoric Acid solution. Lowers pH of water or nutrient solution. Usage amount depends on level of adjustment...usually 1/8 to 1/4 teaspoon per gallon. (Caution: Keep out of reach of children!)

• pH Down 16 oz (pint), $5.99
• pH Down 32 oz (quart), $8.99
• pH Down 128 oz (gallon), $19.99

pH Up

A 9% Potassium Hydroxide solution. Raises pH of water or nutrient solution. Usage amount depends on level of adjustment...usually 1/8 to 1/4 teaspoon per gallon. (Caution: Keep out of reach of children!)

• pH Up 32 oz (quart), $8.99
• pH Up 128 oz (gallon), $19.99

General Hydroponics Dry pH Adjusters

The acid formulation (pH Down) uses food grade Phosphoric acid to lower the pH to the proper level. The base formula (pH Up) is formulated using Potassium Hydroxide and Potassium Carbonate. Add a little at a time when your nutrient pH is too low in order to raise the pH to the proper level.

• General Hydroponics Dry pH Down, 1.5 lb, $19.99
• General Hydroponics Dry pH Up, 1.5 lb, $19.99

Citric Acid

Powder used to lower pH of water or nutrient solution. Citric acid will not hold pH as stable as phosphoric acid, but citric acid is recommended for use in soil gardens or organic hydroponics. Use just a pinch per gallon.

• Citric Acid, 1 lb., $4.99
• Citric Acid, 5 lb., $17.99

Earth Juice Natural pH Up

Use to raise the pH of liquid plant fertilizers and foliage sprays. Professional strength dry crystals.

• Earth Juice Natural pH Up, 2 lbs, $12.99

Meter Calibration Solutions & Batteries

pH Calibration Solution

Use to calibrate your digital pH meter. Most meters can calibrate at both points, or for a single calibration choose the setpoint closest to your average solution pH.

• pH Calibration Solution (pH 4.0), 16 oz, $9.99
• pH Calibration Solution (pH 7.0), 16 oz, $9.99

Electrode Storage Solution

Helps prolong the life of the electrode.

• Electrode Storage Solution, 8 oz, $7.99

Electrode Cleaning Solution

Dip electrode in Part A for 5 minutes, then Part B for 5 minutes, then rinse again in Part A. Increases accuracy and prolongs electrode life! Sold as a set of Part A & Part B.

• Electrode Cleaning Solution Part A (8 oz) & Part B (8 oz), $15.00

Batteries for Digital Pens

Replacement batteries for pH, TDS or EC pens. Pack of 4.

• Batteries for Digital Pens (4), $5.99