Hydroponic pH Management Guide

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. This is the guide I wish I'd had when I started.

## Quick Picks: pH Equipment

The honest truth: A £8 bottle of pH drops prevents more plant problems than any other purchase you'll make. This isn't optional equipment - it's essential.

## Why pH Matters So Much

Plants can only absorb nutrients within certain pH ranges. Too high or too low, and nutrients become chemically unavailable even when present in the water.

This is called nutrient lockout. The nutrients are there. Your plants can't use them. They show deficiency symptoms despite adequate feeding.

Here's what makes it tricky: lockout looks like deficiency. Yellow leaves might mean "not enough nitrogen" or might mean "plenty of nitrogen but pH is wrong." Without testing, you can't tell which.

I learned this by killing three basil plants. Each time I added more nutrients thinking they were hungry. Each time the problem got worse. pH was 7.8 the whole time. The plants were starving in a nutrient-rich solution they couldn't access.

## Target pH Ranges

General range for most crops: 5.5-6.5

This range allows absorption of all essential nutrients. Different nutrients have different optimal ranges, but 5.5-6.5 covers everything adequately.

Crop-specific preferences:

Staying within range matters more than hitting an exact number. Some variation is fine and even beneficial - it exposes roots to slightly different nutrient availabilities throughout the day.

## Testing Methods

pH Drops (around £8-10)

Add a few drops of indicator solution to a water sample. Compare the colour to a chart. Yellow-green means acidic, blue-purple means alkaline, with gradations between.

Pros: Cheap, accurate enough, no calibration needed, doesn't break Cons: Slower than digital, colour interpretation can be subjective, hard to read in poor light

For beginners, drops are ideal. They work reliably, cost little, and teach you the fundamentals.

Digital pH Meters (around £15-40)

Dip the electrode in your solution, read the number. Fast, precise, unambiguous.

Pros: Quick readings, precise numbers, no colour interpretation Cons: Requires calibration, electrodes degrade over time, can give false readings if poorly maintained

Digital meters are worth upgrading to once you're testing frequently. The speed and precision help when managing multiple systems.

pH Test Strips

Paper strips that change colour when dipped. Less accurate than drops for hydroponics - the gradations are too coarse.

Not recommended for hydroponic use. Fine for swimming pools, insufficient for growing.

## Adjusting pH

pH Too High (alkaline, above 6.5): Add pH Down solution

Most UK situations require pH Down. Our tap water runs pH 7-8 typically. Adding nutrients drops it somewhat but rarely enough.

pH Down is usually phosphoric acid based. Add drops slowly - 1ml at a time for small reservoirs. Mix thoroughly. Retest. Repeat until target reached.

pH Too Low (acidic, below 5.5): Add pH Up solution

Less common in UK conditions but happens with some water sources or after nutrient adjustments.

pH Up is usually potassium hydroxide based. Same process - add small amounts, mix, retest.

Critical technique: Add nutrients first, then adjust pH. Nutrients change pH levels. If you adjust pH then add nutrients, you'll need to adjust again.

## UK Tap Water Reality

British tap water typically runs pH 7.0-8.0 straight from the tap. Regional variation exists - check your water company's data if curious, or just test your tap water directly.

Hard water areas have more dissolved minerals, particularly calcium and magnesium. This provides some nutrients but can make pH adjustment more challenging - hard water resists pH changes.

Soft water areas are generally easier to adjust. Less buffering means pH moves more readily.

Whatever your water type, the process is the same: add nutrients, test pH, adjust as needed. Your specific water just affects how much adjustment.

## Testing Frequency

When setting up: Always test after mixing nutrients and adjusting pH.

First week: Daily testing while you learn your system's patterns.

Established system: Every 2-3 days is usually sufficient. Patterns emerge - you'll predict when adjustment is needed.

If something looks wrong: Test immediately. pH drift is the first thing to check.

Kratky systems: Test at setup. Less critical to monitor frequently since you're not adding water regularly.

Recirculating systems: More important to monitor - pH can drift as plants consume nutrients unevenly.

## What to Avoid

Chasing exact numbers: Don't constantly adjust trying to hit 5.8 exactly. Staying within 5.5-6.5 is sufficient. Over-adjustment stresses plants more than minor drift.

**Testing before adding nutrients:** Waste of time. Nutrients change pH. Test after.

Ignoring pH when diagnosing problems: When plants look sick, pH is the first thing to check. Nine times out of ten, that's the issue.

Cheap digital meters without calibration: Uncalibrated meters lie. Calibrate monthly at minimum, weekly if you want accuracy.

Organic pH adjusters for hydroponic systems: Vinegar and lemon juice are sometimes suggested as "natural" pH Down. They work initially but don't hold pH stable and can encourage bacterial growth. Use proper hydroponic pH solutions.

## Troubleshooting pH Problems

pH drops rapidly after adjustment: Your water has low buffering capacity. Add smaller amounts of pH adjuster more frequently, or consider pH buffering products.

pH keeps climbing despite adjustment: Common in hard water areas. The mineral content resists change. You may need to adjust more frequently or consider using rainwater or filtered water.

pH swings wildly: Your nutrient solution is exhausted. Plants have consumed most of the nutrients, leaving unstable chemistry. Time for a complete water change.

pH seems fine but plants still struggle: Check EC/TDS - the nutrient concentration might be the issue rather than pH. Or there may be root problems, lighting issues, or temperature stress.

## Our Recommendations

Start with pH drops. They're cheap, reliable, and educational. You'll develop intuition for your water and system before investing in digital equipment.

Upgrade to digital when testing frequently. If you're managing multiple systems or testing daily, the speed is worth it. Budget around £20-25 for a decent meter.

Always have pH Down on hand. UK water almost always needs lowering. pH Up is less urgent but worth having.

Keep a log initially. Note pH readings, adjustments made, and plant observations. Patterns emerge that help you predict and prevent problems.

Take our quiz if you want recommendations tailored to your specific setup and water conditions.