# Nutrient Concentration (ppm) or Quantity



## trc_pdx (Mar 22, 2004)

Puzzling over something. Let's say I target a specific concentration of a nutrient in a 100 gal. tank, 10ppm, for example. Now I add a 50 gal sump. If I do nothing else, as volume goes up to 150 gal, nutrient concentration falls to 6.67ppm. Still have the same mass/quantity of the nutrient available to my plants, but it exists in a larger volume of water. There is no more bio-load, just more water. And the plants have access to all of the nutrient as the water circulates. Why would I need to add more of the nutrient to maintain the same concentration? I try to answer my own question by making an analogy to me sealed in a room with x ppm of oxygen in the air. Double the volume of the room and now there's 1/2 the oxygen. I think that's a problem for me. I think I need a certain concentration of oxygen in each breath for things to work as they should. But I'm not sure that's a good analogy to how plants take up nutrients. Somebody slap me in the head and explain why I'm being stupid. TC


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## czado (May 26, 2005)

I have never thought about this. Your thinking makes sense to me, and looking at weight does too, for example stating your setup needs, say, a 5g dose of KNO3 for uptake. I would think strong current is important to ensure the nutrients reach the plants. I do not fully understand what Edward has said about luxury uptake, and it may be the factor that changes things.

I dose to ppm and figured I may as well plant the sump, fwiw.


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## plantbrain (Jan 23, 2004)

As long as the plant biomass stays the same, you can maintain the lesser amounts with more volume. 

Regards, 
Tom Barr


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