What EC Should I Run?

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.

Cannabis and high-demand flowering crops (vegetative): 1.2 to 2.0 mS/cm. Flowering: 1.8 to 2.8 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.

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. 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.

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.

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.