To top off or to not top off the res mid week with TDS?

devolv said:

really? can I get some links please?

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devolv said:

for an 8 week strain it costs me including mid week dosing. about 160$ for a 15 gal res each week. putting in a 200gal res would increase my nuts costs proportionally. a 200 gal res with my nutes would run 1435$. big difference in money spent per cycle. If I was using a different nutrient then, sure, maybe. I like my nut line so i'm not going to be switching soon.
another thing. this whole npk in the res thing. you're assuming that the plants feed on npk at a constant rate. I don't think this is true. I think npk is consumed at independent rates. still just adding base back to it has the potential to cause one of the less consumed compounds to become in excess. thus causing lockout.

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Murphio said:

$160 each week!!!!! I hope that was a typo. And to clear up any speculation you may have, plants do not feed on any nutrient at equal rates. Topping off with feed water should not create that much excess of a specific nutrient to cause lockout unless your pH is way out of range, or your ppm"s are too high in which case you shouldn't be topping off with feed water anyway.

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