pH Test Kit vs pH Meter

Why Kratky growers test pH

Choosing between a pH test kit and a pH meter is one of the first decisions a Kratky grower makes. pH measures how acidic or alkaline the water is. Plants can only take up their nutrients when the pH is in the right range, and leafy greens generally prefer slightly acidic water. Your nutrient label usually gives the range to aim for.

You test after mixing the nutrient, and again whenever you add water. In a Kratky container there is no pump moving the water, so a test after mixing and after each top-up is usually all you need. More in Nutrients, pH and Safety.

How a pH test kit works

Liquid test kits use a few drops of indicator in a small sample of water. The sample changes color, and you match it to a chart. Test strips work the same way: dip the strip and compare its color to the chart on the pack.

• Inexpensive and simple
• No calibration and no batteries
• Reading depends on matching colors by eye, so it is approximate
• Good light helps; colored nutrient solutions can make the color harder to read
• Drops and strips run out and need replacing

How a pH meter works

A digital pH meter has a probe that you dip into the solution, and it shows a number on a screen.

• Quick to read, with a precise number
• No color matching
• Needs calibrating with buffer solutions from time to time
• The probe needs careful storage, usually kept moist with a storage solution
• Costs more, and cheap meters can drift if not calibrated

Accuracy in practice

A meter shows more decimal places, but a meter that has not been calibrated can be further off than a drop test. A drop kit is less precise but does not drift. For a Kratky jar of lettuce, knowing the pH is roughly in range matters more than a precise number. As you add more containers or try fussier plants, a calibrated meter becomes more useful.

Side by side

• Cost to start: test kit lower, meter higher
• Ongoing cost: test kit refills; meter calibration and storage solutions
• Speed: meter faster
• Precision: meter higher, if calibrated
• Care needed: test kit very little; meter regular calibration and probe care
• Best for: test kit for one or a few containers; meter for many containers or frequent testing

Which one should a beginner buy?

For a first Kratky garden, a liquid drop kit or strips are enough. They are cheap, simple and reliable. If you find you are testing often, growing several containers or want precise numbers, add a meter later and keep the drop kit as a check.

Using either one safely

pH up and pH down products are concentrated acids or bases. Wear gloves and eye protection, add them a little at a time, stir and test again. Keep test kits, meters, buffers and pH products out of reach of children and pets, and never test by dipping anything into a drink cup. More on safe handling in Nutrients, pH and Safety.

Calibrating a meter

Most meters are calibrated by dipping the probe in one or more buffer solutions with a known pH and pressing a button. How often depends on the meter and how much you use it; the manual will say. Rinse the probe with clean water between solutions, and store it as the manual says, usually in storage solution rather than dry or in plain water.

When to test

• After mixing nutrient into fresh water
• After adding pH up or pH down, to confirm the change
• After topping up with water or solution
• When leaves look pale or yellow without an obvious cause

In a Kratky container, testing at these points is usually enough. See Yellow Leaves on Kratky Plants for how pH shows in the leaves.

Reading a test kit well

Read drops and strips in daylight or a bright white light, against a white background, and at the time the instructions give. Colors can shift if you wait too long. If your nutrient tints the water, compare carefully, or test a sample of plain water first so you know what the colors look like.

Keeping results consistent

Whichever you use, test the same way every time: same sample size, same light and the same wait before reading. Write the result in your grow journal with the date, so you can see how the pH changes over a grow and spot drift early.