What EC Should I Run?

Chris Brubeck. Reviewed March 2026.

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. EC is measured in milliSiemens per centimetre (mS/cm). PPM (parts per million) is another common unit but 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. 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

Seedlings and early propagation: 0.4 to 0.8 mS/cm. Young root systems cannot handle concentrated solutions.

Leafy greens and herbs: 0.8 to 1.6 mS/cm. Lettuce, basil, spinach, coriander, and similar crops are light feeders.

Tomatoes, cucumbers, and fruiting vegetables (vegetative): 1.5 to 2.5 mS/cm. Fruiting crops are heavy feeders and can handle significantly higher EC than leafy greens.

Tomatoes, cucumbers, and fruiting vegetables (flower and fruit): 2.0 to 3.5 mS/cm. EC can be increased to support the elevated demand for phosphorus, potassium, calcium, and magnesium.

High-demand flowering crops and heavy-feeding cultivars (vegetative): 0.8 to 1.4 mS/cm. Flowering: 1.4 to 2.0 mS/cm.

Late flower and pre-harvest flush: 0.0 to 0.8 mS/cm.

How Australian Water Quality Affects EC Management

Melbourne and Sydney tap water typically runs between 0.05 and 0.25 mS/cm. Adelaide tap water is considerably harder, often running at 0.3 to 0.5 mS/cm or higher. Perth water varies by suburb and season and can reach 0.4 to 0.6 mS/cm in high-hardness areas. This matters because the EC on your meter before you add any nutrients is your baseline. If you are targeting 2.0 mS/cm and your tap water already reads 0.4 mS/cm, you only have 1.6 mS/cm of headroom. Always measure your tap water before mixing. For exact regional baselines and hard water strategies, see Australian Tap Water for Hydroponics in the Troubleshooting Index.

How to Measure EC Accurately

EC readings are temperature-dependent. Quality meters compensate for this automatically (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. Calibrate your EC meter regularly using a reference solution. If your meter's readings seem inconsistent even after calibration, see Why Is My pH Meter Giving Inconsistent Readings? in the Troubleshooting Index, the same causes usually apply to EC probes. For the full range of pH and EC testing equipment available in Australia, browse the pH and EC Meters collection. Need a fast answer rather than the full guide? Our Troubleshooting Index covers this and other common problems in a quick-answer format.

Reading Plant Signals Alongside EC

Signs that EC is too low include pale green leaves, slow growth, thin stems, and poor branching. 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. The correct EC is the one at which plants grow vigorously without showing stress. Start at the lower end of the target range and increase gradually based on plant response.

How much EC a plant can actually use also depends on how dialed in the grow space is. The same cultivar in a tightly controlled environment, stable temperature, correct VPD, strong root health, will tolerate and use meaningfully more EC than it would in a loosely managed space. Treat the ranges above as a starting point, and let how well your space is dialed in guide how far you build toward the top of that range. This is the same principle behind why environment and light come before nutrients when solving a grow problem. See The Real Order of Priority in Hydroponic Growing.

If plants show stress symptoms despite a correct EC reading, the cause is often something other than the nutrient solution itself. Check Nutrient Lockout, Cal-Mag Deficiency, and Nutrient Burn vs Transplant Shock in the Troubleshooting Index for the most common causes.

Managing EC in Recirculating Systems

In recirculating systems such as DWC, NFT, and ebb and flood, EC changes as plants feed. 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. Complete reservoir changes every one to two weeks to prevent salt accumulation and mineral imbalances.

Frequently Asked Questions

What EC should seedlings and clones be in hydroponics?
Seedlings and early propagation should be kept at 0.4 to 0.8 mS/cm. Young root systems cannot handle concentrated solutions, and starting low reduces transplant shock and supports healthy early root development. Many growers start with plain water or a very dilute rooting solution before introducing any base nutrient.

Why does EC rise in my reservoir without me adding more nutrients?
When plants drink water faster than they take up nutrients, the nutrient concentration in the remaining solution increases. This commonly happens during hot weather or under high light intensity. Top up with plain water to dilute the solution back to your target EC rather than adding more nutrients.

Why does EC rise specifically when my reservoir water level drops?
The nutrient salts in your reservoir do not evaporate or get consumed at the same rate as the water itself. As the water level falls, either from evaporation or from plants drinking faster than they feed, the same amount of dissolved nutrient is left in a smaller volume of water, so the concentration, and therefore the EC reading, climbs. This is why EC and water level should be checked together, a falling level with no top-up is a reliable early warning that EC is drifting upward even before the reading itself confirms it.

What is the difference between EC and PPM in hydroponics?
EC measures electrical conductivity in mS/cm and is consistent across all meters. PPM uses a conversion factor that varies between manufacturers, so 1000 PPM on one meter may not equal 1000 PPM on another. EC is the more reliable unit for comparing readings across different equipment and feed charts.

How does Australian tap water EC affect my nutrient mixing?
Your tap water EC contributes to the total strength of your nutrient solution. Melbourne and Sydney tap water adds only 0.05 to 0.15 mS/cm, which is negligible. Adelaide tap water can add 0.3 to 0.7 mS/cm, which meaningfully reduces how much nutrient you can add before hitting your target EC. Always measure your tap water first and subtract it from your target when mixing.

How often should I change my hydroponic reservoir?
Every one to two weeks in recirculating systems like DWC and NFT. Regular complete changes prevent salt accumulation and mineral imbalances that build up even with daily top-ups. Between changes, top up with fresh water to maintain volume and dilute any concentration increase from evaporation and plant uptake.