Making the Most of Meters and Monitors

From simple thermometers and light meters to the most advanced refractometer, there are a variety of hand-held meters and monitors to ensure optimal growing conditions for your plants. Typically, though, indoor gardeners pay closest attention to the pH and nutrient levels of their hydroponics solutions so we'll start with those.

pH Levels

If the pH of your nutrient solution is too high (alkaline) or too low (acidic), it can restrict the uptake of nutrients through the roots of your plants. Many different variables such as evaporation, temperature, and amount of light can affect pH levels. As such, frequent monitoring of nutrient solution pH levels is a good idea. pH test kits, meters, and monitors range in price, accuracy, and durability. Less expensive, hand-held meters feature delicate glass probe tips which are dipped into nutrient solution for periodic testing. More expensive models are made to remain directly in the nutrient bath and offer continuous pH readings. Most plants absorb nutrients best in hydroponics solutions with a pH between 6 and 6.7.

Nutrient Levels

Hydroponic gardeners all over the world monitor nutrient levels in roughly the same way-by measuring total dissolved solids in the growing solution-but they have different preferences for the format of their test results. Growers in the U.S. often examine a simple ratio known as parts per million (PPM). High concentrations of salts increase the solution's electrical conductivity (EC) and this is the standard measure used in Canada, Europe, and elsewhere.

Total dissolved solids readings-whether in PPM or EC formats-help to indicate the density of solution which can help to determine when it's time to add nutrients. Temperature can affect TDS/EC meter readings. Like pH testers, TDS/EC meters are available in less expensive, hand-held models and more expensive, continuous-read varieties, too. Finally, it's important to make sure that you read your hydroponics nutrient packaging carefully to make sure feeding indications correspond with the kind of meter you have chosen!)

Light Meters

Plants use a different part of the light spectrum to grow, and some indoor growers use light meters to make sure their plants are getting the most from the light sources provided. Light meters aren't used as often as pH and TDS/EC testers, but they can help you maximize light coverage and bulb performance for your plants. Because light output decreases with age, it's important to check the strength of your bulbs periodically-especially since your electricity bill will be the same even if your lamp is putting out half as much light. Light meters will help you decide when it's time for a new bulb or whether a light mover might be helpful.

Temperature

Simple thermometers are handy for monitoring the temperature of your nutrient bath. Light placement or even a faulty thermostat can cause plant roots to get too hot. Usually, optimal nutrient solution temperatures fall in between 65 and 75 degrees F because water holds oxygen best in this range.

Combination Monitors

It is worth noting that some high-end monitors combine more than one kind of probe-often nutrient temperature, pH, and TDS/EC-in the same diagnostic unit. Many are water resistant and some are even waterproof.

Refractometers

Want to get really proactive? Because it can point to problems long before your plant exhibits any particular symptoms, a refractometer is kind of like a crystal ball. Growers employ refractometers to measure the sugar levels in their plant foliage; high sugar levels in plant tissues indicate strong, healthy growth. Refractometers are especially useful because they help indicate whether or not your plants are getting plenty of nutrients and how well they are using them.