A nutrient mix can look right on the bottle and still land too strong in the reservoir. That is where the EC meter versus TDS meter question matters. Both tools measure dissolved material in water, but EC gives you the direct electrical reading. TDS gives you a calculated estimate in ppm.
For mixing nutrients, tracking reservoir strength, and comparing runoff, use EC as your main number. A TDS reading can still be useful, especially if that is the scale you know, but it only means something when you know the meter’s conversion factor and keep it consistent.
EC meter versus TDS meter: the direct answer
EC means electrical conductivity. Dissolved mineral salts conduct electricity, so an EC meter measures how easily electrical current moves through your water or nutrient solution. More dissolved fertilizer salts generally means a higher EC reading.
TDS means total dissolved solids. Most handheld TDS meters do not weigh every dissolved particle in the sample. Instead, they measure EC first, then multiply it by a conversion factor and display an estimated parts-per-million, or ppm, number.
That difference is the whole issue. EC is the measured value. TDS is an interpretation of that value.
If one grower says their feed is 900 ppm and another says theirs is 900 ppm, they may not be running the same strength. A meter using a 0.5 conversion factor displays 500 ppm at 1.0 EC. A meter using a 0.7 factor displays 700 ppm at the same 1.0 EC. The water did not change. Only the math on the screen changed.
For that reason, record EC when you want clean notes that transfer from one meter to another. If you use ppm, write down the meter scale too.
What EC and TDS can tell you
Neither meter identifies which nutrients are in the water. A high EC could come from a balanced base feed, hard starting water, excess calcium, or a buildup of several minerals. The meter tells you total conductivity, not whether the ratio is right.
That makes the meter a control tool, not a fertilizer recipe. Use it to verify that you mixed consistently, to see how much mineral content your source water brings in, and to watch whether a recirculating reservoir is drifting between changes.
For a lettuce tower, basil reservoir, or tomatoes under an LED, check the water before adding feed. Then measure again after every nutrient has been mixed completely. Check pH after the nutrient solution is at its final EC, because adding nutrients can move pH.
The HM Digital HydroMaster HM-200 portable pH, TDS, EC, and temperature meter puts those readings in one tool. That is useful when you do not want separate instruments for source water, nutrient strength, pH, and solution temperature. Pick one display mode for your grow log. For nutrient work, make EC the lead number and use TDS as a familiar reference if needed.
Start with the water, not the fertilizer
Your starting water sets the floor for every mix. Fill a clean container with the water you plan to use, let its temperature stabilize if it has just come from a cold tap, and measure EC before anything goes in.
A low starting EC gives you more room to build a precise nutrient mix. A higher starting EC means the water already contains dissolved minerals. Those minerals may be harmless, useful, or poorly matched to what your plants need. The meter cannot sort that out on its own, but it shows why a feed schedule may not match the final number in your bucket.
If source water is consistently high in EC or varies widely, reverse-osmosis water filtration can give you a more predictable starting point. When you begin with very low-mineral water, add your complete base nutrient first. Do not start chasing the meter with single additives before the base feed is in solution.
Mix the base nutrient for your medium
The base nutrient carries the main feed. Choose it by root zone, then measure the finished solution with EC.
For potting soil and container vegetables, Bionova Soil Supermix is the base feed to use in soil. Soil has its own mineral reserve and microbial activity, so the EC in the watering can is only part of the picture. Measure the mixed feed, avoid abrupt jumps, and pay attention to how consistently the plants drink and grow.
For coco coir, use Bionova Coco Forte A+B. Mix Part A fully into the water before adding Part B. Then measure EC after both parts are thoroughly dissolved. Coco can hold and release nutrient ions, which is why a runoff EC check can help show whether the root zone is accumulating salts or running leaner than the input.
For recirculating hydroponics and other water-based systems, use Bionova Nutri Forte A+B Hydro. Mix one part completely before the next part, circulate the reservoir, then take the EC reading. In a reservoir, the value is most useful as a trend. A stable EC alongside stable water level tells a different story than an EC that climbs or falls sharply over a short period.
Do not compare the label dose with a ppm target from a different meter and assume they match. Use the base nutrient’s mixing directions, measure EC with your own meter, and keep notes on what the plants receive.
Add minerals one at a time, then recheck EC
Single-mineral products are where an EC meter earns its place. A small correction can change the total strength of the mix, even when the amount looks minor in a measuring cup.
Use Bionova Ca 15 when your water and base program call for an added calcium input. Use Bionova MgO 10 when magnesium needs correction. Add either product to the fully mixed base solution, circulate or stir well, and check EC again before deciding whether any further adjustment is needed.
Bionova Micromix is for targeted micronutrient support. It is not a substitute for a complete base nutrient. Add it only when it fits the crop, water source, and feeding plan, then confirm the final EC rather than assuming a small addition has no effect.
Bionova SiLution is used for soluble silicon. Add it according to its mixing directions and keep the same order every time you mix. Consistent order matters because it makes your EC records useful. If every batch is mixed differently, a number on the display cannot tell you much.
For rooted cuttings, transplants, and young plants moving into their first feed, Bionova Roots is the root stimulator to add within the recommended program. Its presence still belongs in the final solution check. Measure after everything is mixed, not halfway through the process.
As flowering and fruiting plants move into their appropriate later-stage feed program, Bionova PK 13-14 is the targeted phosphorus and potassium additive. Treat it as a specific addition, not a reason to discard your base nutrient program. Mix, circulate, and verify the final EC.
Use runoff and reservoir readings as clues
In coco, collect enough runoff to test a representative sample rather than the first few drops from the pot. Compare its EC to the solution going in. A runoff number well above the input can point to mineral accumulation in the root zone. A number below the input can mean the medium is holding ions or that the root zone is interacting with the feed differently than expected.
Those readings are clues, not automatic instructions. Check irrigation frequency, container dryback, plant age, and the consistency of your input before making a large feed change. One runoff sample can be misleading. Several readings taken the same way are more useful.
In recirculating hydro, measure at roughly the same time each day. Check water level, EC, pH, and temperature together. As plants take up water and nutrients at different rates, EC can move. Top off, adjust, or replace the reservoir based on the pattern and your crop’s feed plan, not a single reading in isolation.
Keep the meter trustworthy
Rinse the probe with clean water after testing nutrient solution. Do not let dried fertilizer sit on the sensor. Calibrate on the schedule in the meter instructions using the appropriate standards, and verify readings whenever a number looks out of character with a fresh mix.
Temperature also affects conductivity. The HydroMaster reads temperature alongside EC and TDS, which helps you avoid comparing a cold sample with a warm one as if they were identical. Test samples at similar temperatures whenever possible.
The useful number is the one you can repeat. Mix in the same order, measure after the solution is fully blended, log EC, pH, temperature, and the products used. That gives you a record you can act on when basil slows down, butterhead lettuce colors up differently, or cherry tomatoes begin drinking harder under the light.
Start with the HM Digital HydroMaster HM-200 portable pH, TDS, EC, and temperature meter, use EC as your nutrient baseline, and let the record from your own garden guide the next mix.
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