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Soil Meters & pH Testing

Garden Meters & Testing Supplies Overview

The advantage for the novice hydroponics grower today is that the science and methodology is already determined and standardized.  This wasn’t the case for the brave pioneers with their primitive ebb & flow systems years ago.

They had to learn everything the hard way and only had a vague, theoretical idea of what works and what doesn’t.  During the early days these growers had to learn exactly how to formulate the nutrient solution precisely to create the ideal growing conditions that would assure hydroponic gardens would thrive.

All that trial and error or guesswork is gone for today’s hydroponic gardener and we now know what to test for, how to monitor and how to accurately formulate the nutrient solution.  One of the great advancements has included accurate, reliable measuring tools.

There is nothing for the newcomer to be overwhelmed by because all of these testing meters are easy to use, and it isn’t all that complicated to adjust your nutrient solution accordingly.

There are three main, basic types of testing you will do.

  • pH (acidity)
  • EC (electrical conductivity
  • TDS (total dissolved solids

What are these, why are they important and how are we able to monitor them?

Let’s begin with the simplest and most widely known.

The acidity of your solution or pH

Almost everybody has heard of pH or the acidity of soil or growing medium used for plants. The pH levels are even more important with hydroponic gardening.

A pH reading of 7 is universally recognized as be neutral, meaning, it is neither acidic or alkaline. The further up the scale we move from 7 up to 14 the more alkaline or “sweet” the medium is and conversely a reading lower than 7 indicates more acidic conditions.

Plants grown in hydroponic gardening prefer a slightly acidic reading of between 5.8 to 6.2.  Generally speaking, pH is so easy to read and so very common in all forms of gardening that there are very simple testing methods available.

The simplest method is a basic pH paper that changes color depending on the acidity of the medium.  While this method is great for the conventional gardener it is not suitable for accuracy required in hydroponic gardening.

The readings on pH paper are vague and most often only readable as approximations and not exact numbers.  Today there are literally thousands of great electronic pH meters available for every type of use.

It can get a little confusing, though, regarding which one to purchase because they can range in price anywhere up almost a grand. My view on pH meters is that pH is so simple to test that for the beginner to spend $1,000 on a meter that thing better be able to also clean the glass on the greenhouse and make you dinner on top of it.

Testing pH just isn’t that complicated to justify such an expenditure when you’re first starting off and there are adequate meters out there that cost far less.

Milwaukee brand is one of the leaders in hydroponic meters and they have pH meters that range from the very basic at around $50.00 on up to more accurate models in $200-$300 range.  There are other brands out there such as Luster Leaf that cost far less, but you’re not going to get a reliable or durable digital meter for $10 to $12.00 so be realistic about it.

The best way to start with pH meters is to begin more modestly and upgrade as your experience and garden grow to a more serious level.

Electrical conductivity or “EC”

This is one area in hydroponic gardening that can get real complicated, real fast so keep that in mind.  It can all be simplified if you truly understand just how we measure electrical conductivity.

To give you a fuller understanding on this all liquids have some level of electrical conductivity or EC as we will refer to it here on out.  

In hydroponics the richer the nutrient solution the more it conducts this current while conversely, the more diluted the solution the less current it will carry.  In most cases, for most garden plants we’re looking to maintain an EC reading of right around 1.5.

There are exceptions to this, however, and if herbs like basil, for example, are going to be your crop of choice, they do require a higher EC of about 2.0 or slightly more.  Lettuce, on the other hand, is slightly lower at 1.2 to 1.3.

The whole reason more nutrients in your solution increase EC really comes down to the levels of soluble salt.  These ions create conditions which more readily carry an electrical current and therefore increases it.

What you’re measuring when testing for EC is known as “siemens.”  Specifically, you’re measuring millisiemens per centimeter.  

Where the complication sets in is that Europe measures EC in a completely different way than growers in the US do.  European hydroponic gardens are measuring actual siemens where in America the preferred measurement is in parts per million or ppm.

However, the end measurement is always the exactly same and essentially is telling you how much nutrient is in your nutrient solution.

Keep in mind however, that it is far easier to boost the nutrients than it is to dilute it.  Start off on the conservative side, slowly increasing the nutrients from that point.

Just as with the pH meters there are some cheapo products out there that are plain junk and you are only throwing your money away.  Some of the more decent brands are Hanna, Omega or Oakton.

You can expect to pay anywhere from $95.00 on up to $250.00 for accurate, modestly priced brands.  Again, be prepared to upgrade as your operation and expertise expand but as a beginner these models will serve you quite well.

TDS- total dissolved solids

Let’s word this as simply as possible.

A TDS meter essentially measures the total concentration of your nutrient solution.  It does this by running a very small electrical current between the electrodes which will give you the desired reading.

What TDS comes down to is that while just plain water carries an electrical current it doesn’t really carry all that much. The amount of electrical current is increased by the amount of the dissolved solids within the nutrient solution.

A TDS meter will accurately measure this current and therefore tell us just how much of our nutrient solution is dissolved solids.

The actual desirable levels of TDS as measured in ppm (parts per million) for plants grown hydroponically varies a great deal. It ranges a great deal from beans which require a modest 1200 ppm to heavy feeders like cabbage at 2,100 ppm.

Hydroponically grown cannabis ideally should be around 500-600 ppm for seedling clones and around 800-900 for mature plants up to 1,100 during the flowering stage.

Because there is no one standard for desirable TDS for most plants an excellent and accurate meter is the preferred route to go.  

Again, don’t try to cut corners on price with especially a TDS meter because it is just too important.  Omega, Oakton and Milwaukee all have reasonably priced and accurate models ranging from around $100.00 to the $200.00 range.

When your business grows you can upgrade your meter to the Autogrow or Bluelab systems, the Roll Royce & Lambo of garden meters.

Our whole point here is to help you gain a better understanding of hydroponic meters and why they are important.  We want to see everybody succeed and thrive as part of the growing hydroponic community.

If you need any help, send us an email or call us. Happy growing!