Hydroponic pH Management Guide

Not sure which setup is right for you?

pH might be the most important number in hydroponics. Get it wrong and plants starve even when surrounded by nutrients. Get it right and everything else becomes easier.

Why pH Matters: Plants can only absorb nutrients within certain pH ranges. Too high or too low, and nutrients become chemically unavailable. The plant shows deficiency symptoms despite adequate feeding.

This is called nutrient lockout. It's the cause of most "my plant looks sick" problems.

Target pH Ranges:

Most vegetables and herbs: 5.5-6.5 Leafy greens: 5.5-6.0 Tomatoes and peppers: 6.0-6.5 Strawberries: 5.5-6.2

Staying within range matters more than hitting an exact number. Some variation is fine and even beneficial.

Testing Methods:

pH drops (around £5-10): Affordable, reasonably accurate. Add drops to a water sample, compare colour to a chart. Good enough for most hobby growers.

Digital pH meter (around £15-40): Faster, more precise. Requires calibration and electrode care. Worth it if you're testing frequently.

pH test strips: Less accurate than drops. Not recommended for hydroponics.

Adjusting pH:

pH too high: Add pH Down (phosphoric or citric acid) pH too low: Add pH Up (potassium hydroxide or similar)

Add small amounts. A few drops can shift pH significantly. Mix thoroughly and retest before adding more.

UK Tap Water: British tap water typically runs pH 7-8 and contains variable minerals. Adding nutrients usually drops pH somewhat. Many growers find they mostly need pH Down.

Hard water areas (high calcium/magnesium) may need additional consideration. Soft water areas are generally easier to manage.

Testing Frequency: Check pH when you first mix nutrients. Check again every few days. Plants and microbial activity change pH over time.

If pH swings wildly, your nutrient solution may be exhausted or contaminated. Time to change it.

Common Mistakes:

Chasing exact numbers: Don't constantly adjust. Let it drift within range.

Testing after adding nutrients: Always add nutrients first, then adjust pH.

Ignoring pH entirely: The single biggest beginner error.

Our Recommendation: Start with pH drops. They're cheap and educational. Upgrade to a digital meter once you're committed and testing frequently.

Check pH before panicking about plant problems. Nine times out of ten, pH is the culprit.

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