DWC water levels

Budley Doright said:

^^^ how do you know after 7 weeks that your nutrient ratio' are not totally out of whack? I actually have never added back other than when away and just have the girlfriend top up the Res. Always was worried that things would get out of balance re nutrients.

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I check the water level, ph, and ppms daily.
After I top off with water, I adjust ph (if necessary) and ppms accordingly.

Sorry, I think I misread your comment.
By ratio, I now think you mean NPK ratio. If this is the case, my plant currently drinks about 12litres a day, so when I adjust it, I use my desired ratio. As for the ratio that is already in the container, I generally don't have to worry because the plant goes through so much water, so it's pretty much always gonna be that ratio. Also, I can tell what my plant is lacking (or getting too much of) by looking at it.

I can't tell the difference between a lot of the deficiencies, they all look alike to me lol.

Budley Doright said:

^^^ how do you know after 7 weeks that your nutrient ratio' are not totally out of whack? I actually have never added back other than when away and just have the girlfriend top up the Res. Always was worried that things would get out of balance re nutrients.

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This is such a completely valid question, and I'm surprised more people don't ask about it (probably because they don't know about it)? Anyways, I don't change my water at all. I just top up. My theory is the plants are always sitting in water where the nutrients are available, so the ratio might not be as important. I used to calculate npk for soil and organics, but I feel it's unnecessary in dwc (although this might not be true in other hydro methods). I just haven't noticed a difference in dwc to warrant me worrying about it, and draining my system only to refill it wasting nutes and water.