Mixing Base Nutrients
By Hydro Harvest
- 02 April 2025
Right at the heart of your grow is your base nutrient. This feed provides your plants with the core, essential elements for growth and yield. The bulk of your nitrogen, phosphorus, and potassium as well as multitudes of micro and trace elements will come from the base nutrient.
As you can imagine, anything that is so central to your success is worth preparing and maintaining properly.
The good news is that with a bit of easy-to-use kit and some straightforward, simple-to-apply advice you’ll be able to prepare a grow-maximising base nutrient solution in no time.
We take you through the method right here. First off, we need to consider the ingredient that makes up the bulk of your base nutrient solution – water.
Water
Needs to be understood. All good growers know their water. Why? Because every water supply has unique characteristics. And these characteristics need to be factored in when choosing and preparing plant nutrients.
Wherever you are in the country, or indeed the world, your water supply has its own level of EC (Electrical Conductivity). EC is basically a measure of the mineral strength within your water. Having an EC level needn’t be a problem. It needn’t stop you feeding your plants the way you want to feed them. You just need to know your EC and work with it.
If you don’t know your EC level, you can easily end up:
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- Buying the wrong type of nutrient
- Applying that nutrient at levels your plants can’t absorb
- Slowing or damaging plants by under- or over-feeding
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The good news is that EC levels are easy to understand, monitor, and master.
EC Levels
You might assume tap water has an EC of 0.0. Tap water does not have an EC of 0.0. Unless you’ve specially filtered it using a Reverse Osmosis (RO) system your water supply will have a readable EC level straight from the tap.
Measuring EC is easily done. One monitor above all others rules the roost where this exercise is concerned. Yes, it may cost a few quid, but a Bluelab Truncheon is an absolute grow room essential for checking Electrical Conductivity. It’s accurate, waterproof, useful for mixing, and properly maintained it will last you for years.
EC and Nutrient Types
If your water supply measures below 0.4 EC, you are in a soft water area. You should choose a Soft Water version of your base nutrient.
If you are in a soft water area you also need a CalMag solution to get your ‘baseline’ tap water EC level up to 0.4. Add CalMag after de-chlorinating (see below) but before adding your nutrients (see further below).
If your water supply measures 0.4 – 0.9 EC, you are in a hard water area. Simply choose a Hard Water version of your base nutrient.
Note. If your water supply measures anything above 0.9 EC, you are potentially in need of a Reverse Osmosis filtration system to strip your water supply bare of all mineral content. Then approach it as if in a soft water area.
Before you start mixing up there’s one more thing to do to get the best from your water.
Dechlorination
Tap water contains chlorine. Chlorine can kill off the beneficial bioactive cultures in your grow media, feeds, and additives. Therefore, it is necessary to neutralise the chlorine in your water supply before mixing any nutrients in it.
Some growers will insist that leaving tap water to sit overnight will suffice. But if you want to be sure then get yourself a water conditioner such as Ecothrive’s Neutralise. This stuff is produced by certified and celebrated organic growers, so you know it’ll be safe and effective. You may not be growing organically but that doesn’t really matter. Neutralise will do an excellent job of getting your supply dechlorinated and ready for use.
If you’re in a soft water area add your CalMag now and recheck your EC.
EC levels checked. Correct nutrient selected. Water dechlorinated. CalMag added (if necessary). Time to get mixing.
Mixing Base Nutrients
The Theory
As you add your base nutrient to the water the EC level of the solution will increase.
You’ll be looking to add base nutrient and increase EC until you hit an optimum number. So, how much nutrient should you put into your water / how high should your EC be?
This will depend upon:
- The starting EC level of your tap water
- The type of plants you’re growing
- The plants stage of growth
A) – You will know because you’ll have measured your tap water EC levels. The feed chart that comes with your nutrient will tell you what to use in relation to B) and C).
When it comes to adding nutrients, you must factor the EC level of your tap water into the EC level quoted in the feed chart.
So, say your tap water EC is 0.4.
And your feed chart quotes a target EC of 1.4.
You want your final nutrient solution (tap water + nutrient) to be EC 1.4.
Don’t go to EC 1.8. there will be elements within an 0.4 EC tap water that act as food.
The Method
Mix your base nutrients in one at a time, thoroughly, and by the numbers. This basic method of mixing remains the same regardless of your brand of nutrient, type of nutrient, or how many parts your nutrient has.
Multi-part base nutrients that come from separate bottles have been packaged that way for a reason. They are only designed to combine when fully mixed in water. Do not pour all the parts in together and mix. This risks all manner of reactions that will do your crop no favours whatsoever. It’ll also make the nutrient more difficult to mix thoroughly.
Mixing Thoroughly
Get whatever stirrer you’re using deep, deep down to ensure a uniform mixture. Only by doing this can you get a reliable number on your target EC.
Steady as she goes
Keep monitoring your EC levels as you go. It is far easier to get EC levels right if you add nutrients gradually, working bit-by-bit towards your magic number.
If you do overshoot with EC levels, you can add more water to dilute things down. But remember that some / all the above processes (measuring, dechlorination, CalMag etc, etc) might be necessary to get your diluting water up to spec. It is far easier to undershoot and add a little feed at a time.
Once you’ve got your EC levels where you want them it’s time to optimise your prepared base nutrient for absorption. For that you’ll be wanting to measure and adjust your pH levels.
pH Levels
The pH level of a nutrient solution dictates how easily and completely it can be absorbed. You want the best possible rates of comprehensive absorption to maximise the effectiveness of your inputs, to stimulate growth, and to deliver healthy, heavy yields.
So, what pH level should you aim for and how can you adjust it?
Target pH levels will depend a little on the cultivation system and the grow media you’re using. But generally, you want:
- pH 5.5-5.8 for hydro based grow media (rockwool or clay pebbles)
- pH 5.8-6.0 for coco-based grow media
- pH 6-6.2 for soil-based grow media
Measuring the pH of your prepared nutrient solution is a doddle. Decent monitors require no complex math’s on your part – it’s a simple case of dip-and-read. Adjusting your pH is only slightly more involved.
Note: If you are adding beneficial microbes such as Plant Magic Granules, plant Success Great White, Mykos, or Azos to your grow ALWAYS add them after the pH has been adjusted. Otherwise, the effectiveness of these microbes will be limited or wiped out by contact with the strong acid or alkaline content of your pH adjuster.
pH Adjustment
To adjust pH, you’ll need a bottle of pH Down, a bottle of pH Up, a jug, and a pipette or syringe.
Scoop a litre of your base nutrient mix into the jug. Depending upon the adjustment you need to make add the pH Down or Up to the jug using your pipette / syringe (quantity as directed by the manufacturer). Stir the contents of the jug and then return the contents of the jug to your main container of base nutrient mix.
Stir your main container of base nutrient mix for at least a minute. Then check the pH level. This will ensure that the pH is adjusted throughout the full batch.
Never add drops of pH Down or pH Up directly into your nutrient solution.
As with nutrient solutions, work gradually. An incredibly tiny amount pf pH Down or Up goes a very long way, even in a large amount of prepared nutrient solution. Mix in the pH Down or Up and test the pH level repeatedly until you get it to your satisfaction. Put the solution to use, then wait for up to 24 hours, measure the pH again, and correct again. You will almost certainly to correct it again owing to ‘pH drift’.
Note: that the pH of a solution will rise naturally over time as carbolic acid escapes in the form of CO2. This upwards drift will be accelerated if you are bubbling the mix with an airstone, as constantly the surface tension allows CO2 to escape.
pH Drift
Reactions with grow media in your cultivation system, the water in your nutrient solution, and the nutrient within your nutrient solution will cause pH drift in the first 24 hours. This is easily remedied with a little more pH Down, cautiously applied.
pH is likely to rise repeatedly over the first three days before settling down. As long as you’re monitoring and countering this, you’ll be fine.
Monitoring and Maintaining Levels
By checking your EC and pH levels continually you’ll give yourself the best chance of maximising growth, yield, and the effectiveness of your inputs.
When you check your EC, you’ll see how your plants are feeding. If the EC has remained as it was when the solution was mixed, then you’ve got the balance just right. On the other hand, if the EC has dipped, then you need to up the nutrient concentration slightly – by 0.1 at a time. Finally, if the EC has risen then some dilution with EC-checked, dechlorinated, CalMag-balanced water is required.
Testing for pH will help ensure you’re always on top of nutrient availability and prevent deficiencies. If your plants do have visible problems a quick check of the nutrient solution pH can be a dead giveaway as to what’s wrong. If the pH is off your plant won’t be able to access certain minerals and often that shows in the leaves, stems and overall growth.
Always test before topping up a solution and if it’s not used up then ideally replace your solution completely once a week. Remember, if you do top up, take the same preparatory steps as you did the first time you mixed up your base nutrient.