When you grow cannabis in hydroponics, it is common to monitor the EC of your feed, and your runoff, to get a rough idea of how much your plant is eating. The best EC for cannabis plants, is not set in stone, and each strain, and even each phenotype will prefer different levels of EC.

The only way you can really tell what the best EC for your cannabis plants is, is by monitoring what you are feeding them, and comparing it with what they are giving back in runoff, or changes to your reservoir.

In this guide we will go step by step, and explain how you can find the best EC for your plants. This will help you feed them what they need, when they need it.

Knowing how to find the best EC for your cannabis plant will keep your plants healthy and happy throughout their whole grow, which in turn will give you a better final product.

If you have any questions about finding the right EC for your cannabis plants, then feel free to ask for help in our cannabis growers forum

Contents

• What is EC
  • EC Meters
  • EC and PPM Conversion
• Best EC for Growing Cannabis in Hydroponic Systems
  • What EC to Feed your Plants in Hydro
  • PH and EC Fluctuations in the Reservoir
  • Finding the Right EC for your Reservoir
  • Leaching Nutrients
• Best EC for Growing Cannabis in Coco
  • What EC to feed Cannabis Plants in Coco
  • How EC works in Coco
  • The Dangers of EC Spikes
  • How to Test the EC of Coco
    • Test your Nutrient Solution Before Feeding
    • Testing the Runoff After Feeding
  • Finding the Best EC for Cannabis Plants in Coco

What is EC?

Growing cannabis in hydroponic systems like DWC, NFT, and coco, is usually done with "salt based nutrients". These nutrients will be added to water, at lets say, 1ml per litre.

As the salts are added to water, the water will become more conductive, meaning that an electrical current can pass through it easier. As more salts are added, the electroconductivity of the solution will rise. This is what EC is.

By monitoring the EC (Electro Conductivity) of your nutrient solution, you will have an idea of how much of the salt based nutrients are available to your plant, in turn you will know how much you are feeding your plant.

To check the EC of the nutrient solution for your plants, you need a good reliable EC meter.

EC Meters

You need to be sure that your readings are accurate when you test the nutrient solution. Accuracy and reliability are important, so you should buy from brands that are used by cannabis growers, and are trusted.

Don't cut corners with the EC meter, get the best one you can afford, knowing the EC of your feed will keep your plants healthy and happy, it is worth investing in a good EC meter.

EC Meters for Hydroponics

EC and PPM Conversion

In some cases, you may have a "PPM" meter, instead of an EC meter. EC is seen as a more accurate way of testing the strength of a nutrient solution, and it is used by growers all over the world.

The problem with PPM meters, is that different models will have different readings, depending on their country of origin. They have certain conversion ratios that can be confusing.

Sometimes you may find guides across the internet that use PPM instead of EC. The problem is you're not really sure what PPM conversion ratio the guide you are reading is using, and how it compares with your PPM meter.

It's best to stick with EC, as that is a flat reading no matter what meter you use.

Here is a chart, that can help you convert PPM into EC, it will also show how confusing the different PPM ratios can be. Keep it simple, and use EC:

Best EC for Growing Cannabis in Hydroponic Systems

In full hydroponic systems, such as DWC, NFT, and other methods where the roots are suspended in water, plants are said to be able to take a higher EC, than a plant in soilless mediums like coco.

This is because plants growing in hydroponics, will have an airstone in the root zone which will provide air directly to the plants roots. This helps the plant eat and drink more.

But, this doesn't mean you can push your plant full of nutrients, and hope it grows bigger, a plant can only eat a certain amount. You have to find the right balance, and feed the right amount of nutrients to the plant.

What EC to Feed your Plants in Hydro

I can't tell you the answer to this question, nobody can. Each plant, from each seed, in different environments, will use their nutrients differently. The best way to find out the best EC for your cannabis plant, is by monitoring what you're feeding the plants, against what they are giving you back in runoff.

To put it simply, if the EC of your feed is 1.0, and the EC of the runoff rises to 1.4, your plant is not using all of the nutrients, and you're over feeding it.

If the EC of the runoff falls, to 0.7, then your plant needs more nutrients. What you're looking for is the run off to come out at around the same EC as it goes in.

PH and EC Fluctuations in the Reservoir

Some hydro growers will be using a "recirculating system", where the runoff after feeding, will be redirected into the nutrient tank (reservoir).

In situations like this, you can monitor the EC and pH of the reservoir, to help find the best EC for cannabis plants.

If the water level in your reservoir is falling, then your plant is drinking, this is a good sign. As the plant drinks, it will take in some of the nutrients available to it. This will change the EC and pH of the nutrient solution.

What you are looking for, is a fall in water level, and at the same time, the pH and EC of the water stays stable.

This can be done by monitoring the EC over a few days and making slight adjustments to get the balance just right.

Finding the Right EC for your Reservoir

First off, you need to find out what your BG EC is (background EC). This is the EC of the water you're going to use, before any nutrients are added to it. This will count towards your final EC.

If the BG EC is over 0.6, you should consider using reverse osmosis water, or diluting the water with mineral water to reduce it.

For seedlings: use a very small amount of nutrients, that increases the EC by just 0.2 points. Feed this nutrient solution to your plants, in the recirculating system, and then monitor the EC and pH levels after 24 hours.

If the EC falls, then increase the EC of the reservoir by 0.2 points. If it has risen, reduce the EC by 0.1 point.

You continue this as the plant grows, until you find a nice steady balance. Don't push it too hard, it is better to under feed a cannabis plant than over feed one. Watch the EC and pH, and adjust accordingly.

When you find the right levels, and everything is stable, your plants will have access to the right levels of nutrients, and it will grow healthy and happily

Leaching Nutrients

In some situations, the EC of the nutrient solution is way too low, and nutrients will leach out of the plant, and into the water. This will raise the EC of the nutrient solution, but in fact, the plant is losing food.

This tends to happen only when there are big changes in the EC of the nutrients. The plant and the water, find balance, and there will be a certain amount of food in the plant, that is equal to that in the water.

If too many salts are removed, the nutrient level of the plant is higher than the medium, and nutrients will start moving from the plant and into the water. This can expressed as deficiencies, but the EC will show signs of over feeding. So be careful of this factor.

If you have reduced the EC of your feed by more than 0.4 points, the first test may show a slight raise in EC before it levels off on the second test after another feeding.

Consistency is important. Tiny changes is what is best, so you can monitor the effects. Too much of a change in EC either way can shock the plants, so gradual changes should be made, unless there is a major problem.

From seed, you can follow the plant as it grows and raise the EC as it is needed. But if you're checking EC for the first time on bigger plants, then you need to monitor the levels for a couple of feeds to get an idea of the right levels.

Then you can adjust in small increments in the direction you want the EC to go.

Best EC for Growing Cannabis in Coco

Though coco is a form of hydroponics, it is treated a little differently, as it is not as easy to monitor the EC as it is in a hydroponic system.

After watering your cannabis plants in coco, there will be run off, which is drained away, and then, the coco will begin to dry out.

The plants will drink the water and absorb the nutrients, and the water will also evaporate. When it does, it leaves salts behind, and can cause EC levels to rise quickly in the medium.

Coco should be kept saturated at all times to prevent EC spikes, and these need to be taken into account when testing the feed to find the best EC for your plants.

What EC to feed a Cannabis Plant in Coco

You should always start a seedling off at a very low EC. As the roots form, and the plant grows bigger and heads into veg, you can monitor the feed to find the best EC.

Start off, with just 0.2 points over your BG EC, and monitor the run off from there. You should water at least once a day! Stay consistent, and do it at the same time everyday, about an hour after lights come on if possible.

Feed the seedlings, and collect the runoff as it flows out of the pot. Test this water, to find out what the EC level is.

If it is lower than the feed you have been giving your plants, then increase the EC of the next feed by 0.2. if it is higher, than reduce the EC by 0.1.

Monitor the EC going in, and coming out like this for a few days, and your plant will tell you what the best EC is.

How EC Works in Coco

As you water your cannabis plants in coco, the nutrient solution will wash through, and push old salts out.

Lets not get too complex but, as fresh salts are added, they carry an electric current, this helps them stick to the roots, like your hair does to a balloon. As the nutrient ion is used, it loses its charge too. When new nutrients are introduced, the ones with the weaker bond, get washed away, and the new ones replace them, and the process continues.

Old salts will be washed out with the run off with every feed. If they are not, they will build up in the coco, and you will see a salt build up. This will cause your plants to be sitting in a medium with too many salts, and it can burn them.

You need to have at least 10% run off with every watering when you grow in coco. And you should water everyday. As the plant drinks the water, and moisture evaporates from the pot, the salts will be left behind. This is another way of causing an EC spike that can cause problems with your grow.

The Dangers of EC Spikes

Your plant, and grow medium, will find a steady balance between each other. If there are sharp changes, there can be many problems that arise. As the water in the medium is used by the plant, and evaporates, salt based nutrients are left behind. The drier the medium gets, the more the EC will rise.

This can cause damage to your plants roots and force your plant to take more nutrients than it needs via a process called osmosis. In worst case scenarios, an EC spike can damage the roots to the extent where they can no longer take in nutrients.

If the nutrients in the medium are at a higher EC than what is in your plant, the nutrients will force their way into the plant, causing nutrient burn and excess.

If the EC of the medium is lower than what is in the plant, the plant will leach nutrients into the medium, and it can cause deficiencies. Keep the medium saturated, and always have at least 10% run off with every feed.

Consistency is important, small gradual changes are advised, anything too quick can cause damage to the plant and cause shock.

If at some point you need to flush in hydro and coco, then flush with plain water at the correct pH, but always restore the medium to the correct EC and pH straight afterwards. Only ever feed just water, when you're flushing before harvest.

How to Test the EC of Coco

Firstly, you should know the EC of the feed you are giving to your plants. This will be your background EC plus any nutrients you have added to the water. For Seedlings, it should be your BG EC plus 0.2 EC of base nutrients.

Feed this to your plant, and wait 24 hours, but watch the plants for any sign of changes. Now, you need to feed your plant with a nutrient solution that was the same as yesterdays, same EC, same pH. Get around 10% runoff, and collect it as it comes out of the pots mid flow.

Test this water, and find out if the EC is higher or lower than the feed going in. If it is higher, then you may be feeding your plants too much, and the EC of your feed should be reduced. If it's lower, your plant is using up more than you're giving it, so it needs more nutrients to stay well nourished.

Testing your Nutrient Solution Before Feeding

It is important you get a good, correct reading of your feed, before it is given to the plants. For the best results use a good EC meter, and let your feed sit for a few minutes after mixing before you test it.

Letting the solution sit, will allow the salts to properly dissolve and disperse through the water. This will improve the accuracy of the reading.

If you go slightly over your desired EC, then add more water to dilute the solution. If you're below it, add small amounts of nutrients until the level is right.

Stir well, let it sit for a few minutes, then test it. When you're happy, you can adjust the pH and feed it to your plants.

Testing the Run off After Feeding

After watering your plants, your trays will fill up with water, this is your run off. It has passed through the medium, and replaced old, used salts, with fresh new ones.

This should be collected as it is coming out of the pots. If it is left to sit in trays, it can pick up old salts from them, and alter the actual EC, so your reading will be inaccurate.

Try and collect the runoff as it exits the pots, and take your reading from there.

Finding the Best EC for Cannabis Plants in Coco

By monitoring the EC and pH of the feed before you give it to the plants, and then monitoring the EC and pH of the runoff, you can figure out if your plant is being overfed, or under fed.

You are looking for a stable EC, and a stable PH, with around 10% runoff. This means, you want the EC and pH to come out the same as it went in, or just a little higher then it went in.

If the EC of the runoff is coming out lower than what you are feeding the plants, then you should increase the EC of the next feed.

On the other hand, if the EC of the runoff is higher than the EC of the feed, then you're giving your plant more than it needs, and you should reduce the EC to prevent toxicity.

Less is more! Follow what your plant tells you, this is the best way to find the best EC for a cannabis plant. Don't over do it, it is much easier to fix an under fed plant, than it is to fix an over fed one. Keep the EC low unless your plant asks for more.

To Summarize EC for Cannabis Plants

With small incremental changes and regular testing, you can find the best EC for cannabis plants easily. There is no easy answer as the best EC will differ, depending on a lot of factors. Get to know your plant, and understand what the EC and pH fluctuations mean.

When you have found that correct leve, you will see how much healthier your grows will be in the future.