Top off daily with *half strength nutrients, alternating days topping up with plain water. Change the entire reservoir with fresh solution every ten days to two weeks. (*half the strength of your current new reservior starting strength)
Why should you?
One problem in hydroponics solution maintenance, as water is being taken up by the plants as well as evaporating out of the solution, the concentration of nutrient salts in the solution becomes gradually stronger, sometimes to the point of certain elements becoming toxic to the plants. The TDS will always become stronger as water is taken away from the solution.
Another problem, is that hydroponically grown plants will take up what they need as they need it from the nute solution. A nutrient solution left alone will end up lacking key nutrients, with a build-up of *toxic levels of other key nutrients. *Toxic in the solution, as well as in the plants.
The only way around these problems for the average hydroponic grower, is to practice sound reservoir topping off procedures. The most widely accepted maintenance method, involves daily topping off and routine reservoir solution replacement. IE: Topping off the reservoir daily with a nutrient solution which is half of the current new reservoir strength, alternating days by topping off with plain water and finally, changing the entire res solution at least every two weeks.
Changing the reservoir solution every two weeks, will give the plants a fresh and well balanced nute mix, which has not been altered by the plants nutrient uptake.
*Many scientific studies have been performed, which demonstrate these facts by GCMS testing of the nutrient solution contents and the nutrient salts contained within the actual plant tissues, as the plants "take-up" the specific nutrients in the solution.
Plants will take up excessive levels of some nutrients, leaving the solution lacking in certain key nutrients. Just like a puppy would make him/her self sick if it were allowed to feed from a bottomless food bowl, plants grown hydroponically can harm themselves with nutrient deficiencies, lockouts and overdoses, if allowed to continue feeding without some control over whats available in the "food bowl".
***Reference resource... (Click it)
Nutrient Management in Recirculating Hydroponic Reservoirs by Bruce Bugbee
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