EC is one of the two numbers that every hydroponic grower needs to get right. Get it wrong and nothing else in your program compensates for it. Too low and plants are underfed and slow. Too high and roots stress, uptake locks out, and plants show symptoms that look like deficiencies even though the reservoir is full of nutrients.
This guide covers what EC measures, the target ranges for different crops and growth stages, and how to adjust for Australian water quality and growing conditions.
What EC Actually Measures
EC stands for Electrical Conductivity. It measures how well your nutrient solution conducts electricity, which correlates directly with the concentration of dissolved ions in the water.
In practical terms, EC tells you how strong your nutrient solution is. A higher EC means more dissolved nutrients. A lower EC means fewer.
EC is measured in milliSiemens per centimetre (mS/cm) or microSiemens per centimetre (µS/cm). Most hydroponic growers use mS/cm. The two scales differ by a factor of 1000, so 1.0 mS/cm equals 1000 µS/cm. Make sure you know which unit your meter is displaying before comparing readings to a feed chart.
PPM (parts per million) is another common unit, particularly on North American feed charts. PPM 500 and PPM 700 are two different conversion scales used by different manufacturers, which is one reason EC is the more reliable unit for precise nutrient management.
Why EC Targets Matter More Than Nutrient Brand
Growers spend a lot of time choosing between nutrient brands. EC management often gets less attention, which is the wrong priority.
A correctly diluted nutrient solution at the right EC for the growth stage will outperform an expensive nutrient program run at the wrong concentration. EC determines how much of a nutrient solution a plant can actually access. Overfeeding does not deliver more nutrients to the plant. It creates osmotic stress at the root zone that actively blocks uptake.
EC Target Ranges by Crop and Growth Stage
These are the ranges used by experienced growers across DWC, NFT, coco, and recirculating drip systems. Run-to-waste coco systems often run slightly higher EC than recirculating systems because excess solution is not returned to the reservoir.
Seedlings and early propagation
Target EC: 0.4 to 0.8 mS/cm
Young root systems cannot handle concentrated solutions. Starting low reduces transplant shock, supports early root development, and prevents tip burn in seedlings. Many growers start at plain water with a small amount of rooting solution before introducing any base nutrient.
Leafy greens and herbs (full cycle)
Target EC: 0.8 to 1.6 mS/cm
Lettuce, basil, spinach, coriander, and similar crops are light feeders. They respond well to lower EC and become bitter or bolt prematurely when pushed with high concentrations. NFT systems growing leafy greens typically run at the lower end of this range.
Tomatoes, cucumbers, and fruiting vegetables (vegetative)
Target EC: 1.5 to 2.5 mS/cm
Fruiting crops are heavy feeders and can handle significantly higher EC than leafy greens. Vegetative growth requires strong nitrogen availability, and slightly elevated EC supports the rapid cell division and canopy development of early growth.
Tomatoes, cucumbers, and fruiting vegetables (flower and fruit)
Target EC: 2.0 to 3.5 mS/cm
As plants enter flower and begin setting fruit, EC can be increased to support the elevated demand for phosphorus, potassium, calcium, and magnesium. Many experienced growers run at the higher end of this range through peak fruit development and then reduce it in the final weeks before harvest.
Cannabis and high-demand flowering crops (vegetative)
Target EC: 1.2 to 2.0 mS/cm
Cannabis and high-demand flowering crops (flower)
Target EC: 1.8 to 2.8 mS/cm
Late flower and pre-harvest flush
Target EC: 0.0 to 0.8 mS/cm
Flushing with plain water or a low-EC solution in the final one to two weeks before harvest clears residual salts from the plant and growing media. Many growers use a dedicated flushing product like TA FlashClean rather than plain water to actively clear salt buildup from the root zone.
How Australian Water Quality Affects EC Management
This is one of the most important practical considerations for Australian growers and one that North American and European feed charts do not address.
Tap water EC varies significantly across Australian cities and regions. Melbourne tap water typically runs between 0.05 and 0.15 mS/cm. Sydney can be similar or slightly higher. Adelaide tap water is considerably harder, often running at 0.3 to 0.5 mS/cm or higher depending on the source. Perth water varies by suburb and season.
This matters because the EC on your meter before you add any nutrients is your baseline. If you are targeting a final EC of 2.0 mS/cm and your tap water already reads 0.4 mS/cm, you only have 1.6 mS/cm of headroom before you hit your target.
Growers using hard tap water in Adelaide or regional areas need to account for baseline EC in every reservoir mix and reduce nutrient additions accordingly. Running the full feed chart on top of high-baseline water creates solutions that are more concentrated than the chart suggests.
If you are using rainwater or RO (reverse osmosis) filtered water, your baseline EC will be close to zero, which gives you full control but also means your water contains none of the buffering minerals present in tap water. RO water growers typically need to supplement calcium and magnesium separately to compensate.
How to Measure EC Accurately
EC readings are temperature-dependent. The same solution will give different EC readings at different temperatures. Quality meters compensate for this automatically, a feature called Automatic Temperature Compensation (ATC).
Always measure EC alongside temperature and use a meter with ATC for consistent results. The Bluelab Combo Meter measures pH, EC, and temperature simultaneously with ATC, which removes the temperature variable from every reading and gives you an accurate picture of solution strength regardless of reservoir temperature.
Calibrate your EC meter regularly using a reference solution. A meter that has not been calibrated recently will give you readings you cannot trust, which makes EC management impossible no matter how carefully you mix your nutrients.
Reading Plant Signals Alongside EC
EC targets are starting points, not fixed rules. Plants tell you whether your EC is working through their appearance and growth rate.
Signs that EC is too low include pale green leaves, slow growth, thin stems, and poor branching. The plant looks hungry because it is.
Signs that EC is too high include tip burn on new growth, leaf edges curling upward, brown crispy leaf margins, wilting that does not respond to watering, and a general look of stress. The plant is being fed too hard for its current capacity to absorb.
The correct EC for your specific plants is the one at which they grow vigorously without showing stress symptoms. This varies by genetics, root health, water temperature, light intensity, and growth stage. Start at the lower end of the target range and increase gradually based on plant response.
Managing EC in Recirculating Systems
In recirculating systems such as DWC, NFT, and ebb and flood, EC changes as plants feed. When plants uptake nutrients faster than water, EC rises. When plants uptake water faster than nutrients, EC falls.
Check EC and top up with fresh water or diluted nutrient solution daily during active growth. A significant rise in EC between checks indicates the plant is drinking more water than nutrients, which often happens during hot weather or under high light intensity. A falling EC indicates strong feeding activity.
Complete reservoir changes every one to two weeks in recirculating systems to prevent salt accumulation and mineral imbalances that build up over time even with regular top-ups.
A Simple Starting Point
If you are unsure where to start, mix your nutrients to half the strength recommended on the feed chart and check the EC. This gives you a baseline to work from. If the reading is below your target range, increase gradually. If it is already at or above your target, your water has a high baseline EC and you need to reduce nutrient additions accordingly.
Measure before you mix, mix carefully, measure again before you feed. That three-step process eliminates most EC-related problems before they start.
For the full range of pH and EC testing equipment available in Australia, browse the pH and EC Meters collection.