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I was wondering -- a lot of people are dosing NO3 and PO4 2 or more times a week. I used to dose twice weekly. I recently bought a Hach NO3 kit, and found I had around 30-50ppm in my tanks! Now, I find if I dose to 15-20ppm NO3 at water change, I don't need to dose anymore during the week. I find no measureable drop in NO3 levels during the week. I do have well-stocked tanks and feed daily.

With PO4, I dose to around 2-2.5ppm at water change. This does seem to drop a little by week's end. However, I use Red Sea as my kit, and can't vouch for accuracy as with Hach.

Am I correct in the assumption the fish/waste/feedings/tank age are all playing a role in this maintenance of nitrate levels? For micros, as an example, I add 1.5ml of Flourish and 0.75ml of Flourish iron daily (except when I dose the macros) to a 29 gal. (Lighting is 75W; pressurized CO2 25-35ppm.) If I were to increase micros, would I see increase in NO3 and PO4 consumption? How much is too much micros if you have shrimp?

Comments, observations welcome. Thanks.
 

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Bert H said:
I find no measureable drop in NO3 levels during the week. I do have well-stocked tanks and feed daily.
Some people with well stocked and well fed tanks need no additional macro supplementation. Their nutrients are supplied by feeding. If you see no change in macro concentrations you may not need additional supplementation. In your case uptake of nutrients is probably limited by light or CO2 and the fish waste produced matches those levels. This is good, it means you are close to a natural balance. Those who dose daily often have strong lighting that burns off nutrients much faster than their stocking and feeding provides. They need to add more nutrients for their plants.

Try not adding macros and monitor your average daily NO3 change. Then if you find that you use say 2 ppm NO3 each day and run out by week's end, you could add a calculated 2ppm NO3 each day to maintain your NO3 at low but adequate concentrations. The key terminology here is supplementation rather than dosing. You use fertilizers to make sure your plants have enough nutrients to meet your gardening intrests but also use your plants to reduce the toxic byproducts of animal life. The fish are your primary nutrient source, fertilizers supplement deficiencies in that nutrient source.
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Jeff
 
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