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Old 04-25-2017, 06:20 PM
GpsFrontier GpsFrontier is offline
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Join Date: Mar 2009
Location: Lake Havasu AZ.
Posts: 1,855
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Hello strap,
Yes your absolutely right, adding more nutrient solution back to replace the water the plants drink will cause your nutrient concentrations to rise. You should just add plain water back to replace what the plants drink, and you want the water level to stay relatively steady. As the plants drink the water, they don't use all the nutrients in that volume of water, they only use what they need and leave the rest. So when the water level drops because the plants are drinking it, the nutrient concentration rises. That's why you want the water level to remain as constant as possible, to avoid nutrient fluctuations. In hot dry conditions the plants will drink a lot more water than they use nutrients, so your better off with a slightly diluted nutrient solution.

Yes, over time the plants will deplete the nutrients in the water. That's why you do regular nutrient changes. To restore the nutrients and the balance of those nutrients. You can buy an EC/TDS/PPM meter, but I wouldn't waste the money. The only thing you need them to do they can't do. All they can do you is tell you the total volume of what's in the water. Not what is in it, and how much of each element there is.

If you rely on the EC/TDS/PPM meter to adjust your nutrient solution strength, it's just a mater of time before your plants develop signs of deficiency and/or toxicity. Why? Because like I said the plants use what nutrients they need and leave the rest. That means as you replace the used nutrients with fresh balanced nutrients, the nutrients they use less of will begin to build up in the nutrient solution, and the ones they use more of will become depleted. Your EC/TDS/PPM meter cant tell you which are being used and which are not, nor can it tell you what the concentration of each are. It will just be able to give you a total amount.

I know you said you read a lot of articles, and I dont want to add to that list, but I wrote this article to help explain the relapionship between water volume and nutrient consentrations. "What size reservoir do I need"

Bottom line as long as you have enough water volume so your water levels aren't fluctuating a lot and you change your nutrient solution regularly you should be fine. No useless expensive equipment needed. So how often should you change your nutrient solution? That depends on many factors, again why I wrote the previously mentioned artificial. To help explain the the relationship between plant size and water volume, as well as help explain some of the factors that will affect the plants water and uptake. However I typically change the nutrient solution anywhere from every 1-2 weeks, and sometimes even 3-4 weeks. It all depends on plant size, the environmental factors and total water volume.
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