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Discussion Starter · #1 ·
So I started dosing high nutrient fertilizers in my 120g about 2 weeks ago. I just did a test for nitrates and they are about 80ppm. The fertilizer when dosed in the correct amount, the fertilizer adds 7.5ppm to the tank. I don't believe that there are any other contributing factors in the tank other than the fertilizer. Am I dosing too much? Is that level of nitrates ok? I'm not having any problems because of the high nitrates at the moment, just worried if something might happen
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If you've got fish in there you're gonna have to play the water change game. As was mentioned <30 is safe. I'd aim for lower than 20 for long term. I'd say check the ferts using a 5 gallon bucket of water that you'd use for your water changes (be it treated tap or remineralized rodi) and corresponding dosage. I'd be interested in how much it's actually adding to your water.
 

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Discussion Starter · #4 ·
I just did some calculations and I have been dosing for 160g (120g tank 40g sump). However I completely forgot that my sump is only half filled, so I have been dosing 160g worth of ferts for 140g. Would that make a big difference or not?
 

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I'm by far not the person to ask about the calculations on that but it's definitely a contributor, though I think it would still be on the high end with the 20 gallons factored in, I could be very wrong.
 

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Discussion Starter · #6 · (Edited)
Ok. I did a bit more research and found out that I screwed up. I bought dry ferts that I just add 500ml of water to and then dose. They even gave me a handy little container to put the liquid ferts in that shows the amount of ferts I have left. However, the labels on the container go up to 450ml , which Is very confusing because I have to fill it up to 500ml and the labels go up to only 450ml. So I only filled it up of 450 and the ferts are now more potent. Do you think that's enough in combination with the 20g overdose to get my nitrates that high?
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What is the chemical name or formula name of the dry fertilizer that you are dosing? For example: Potassium Nitrate or KNO3.
 

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Ok. I did a bit more research and found out that I screwed up. I bought dry ferts that I just add 500ml of water to and then dose. They even gave me a handy little container to put the liquid ferts in that shows the amount of ferts I have left. However, the labels on the container go up to 450ml , which Is very confusing because I have to fill it up to 500ml and the labels go up to only 450ml. So I only filled it up of 450 and the ferts are now more potent. Do you think that's enough in combination with the 20g overdose to get my nitrates that high?
View attachment 1029128
Your solution is 11.11% more potent than it should be. Don't worry about that. Don't remix it. Just multiply by 0.9 which is the inverse of 1.1111.
I just did some calculations and I have been dosing for 160g (120g tank 40g sump). However I completely forgot that my sump is only half filled, so I have been dosing 160g worth of ferts for 140g. Would that make a big difference or not?
Then you have to adjust by another 14.29% due to the sump capacity overestimate. The inverse of 1.1429 (14.29% overdose) is 0.875. Multiply 90% x 87.5% = 78.75% to get the product of the two errors. The inverse of 0.7875 is 1.2699. That's a 26.99% overdose you have been overdosing. So dose 78.75% or less of what you've been dosing. But first do some water changes and get that Nitrate out of there.

EDIT: Or more simply 1.1111 x 1.1429 = 1.2699 then invert 1/1.2699 = 0.7875 to adjust. I guess 1.2699 is actually the product of the two errors and 0.7875 is the product of the two adjustments. I approached this inside out.
 

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I would not make any decisions based on the API NO3 kit. It can be notoriously off.

The best thing would be to make a calibrated sample and then test the kit. If you need directions let me know.

If you are dosing 7.5 NO3 weekly and performing 50% water changes, the max accumulation is 15.00 ppm NO3. That does not count any tank generated NO3 from fish load. But even then, seems crazy high. I dose 13 ppm NO3 into my 120G loaded with Rainbowfish and my NO3 is usually around 25 ppm.

The Salifert kit is a much better more reliable test.
 
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