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Hello Eveyone,

I have a high tech tank with a pretty high bio load since i keep discus. My Nitrates read at 10-20 PPM depending on the day. Is it necessary to add nitrogen ferts?

The reason i ask is i know that the plants need nitrogen but i'm not sure if its redundant given the bio load in my tank. I dose P and K routinely but am scared to add nitrogen for fear of brining up my nitrates to a point where it becomes problematic for my discus.
 

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I usually keep my nitrates around 10-20 ppm with no ill effects to my plants.

However, I am a little concerned with your stocking; your bioload must be quite high to maintain a nitrate reading of 10-20 ppm consistently...
 

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Never, never trust a test kit unless you first calibrate it with known solutions. And, it takes a lot more than 40 ppm of nitrates to be harmful to fish, so I would ignore the test kit and just dose potassium nitrate as if there were none in the water.
 

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Hello Eveyone,

I have a high tech tank with a pretty high bio load since i keep discus. My Nitrates read at 10-20 PPM depending on the day. Is it necessary to add nitrogen ferts?

The reason i ask is i know that the plants need nitrogen but i'm not sure if its redundant given the bio load in my tank. I dose P and K routinely but am scared to add nitrogen for fear of brining up my nitrates to a point where it becomes problematic for my discus.
At what NO3 from KNO3, not NH4 from fish waste, does NO3 cause any issue for Discus?

Do you know?
Does anyone know?
Independent of other factors?
NH4 is 100X if not more toxic than NO3 and requires no O2 demand for transformation.

So if you start with NO3...it's an entirely different animal.

50ppm is no issue for Discus IME.
I see no reason to go beyond 20-30ppm for plants however.

As far as a plant "upper limit", it's well over 200-300ppm for N and K and P each. Why? Hydroponic solutions used to grow ornamental and aquatic plants is that rich.

As long as you keep the range at 20-30ppm or so, there should not be any issue. If 10-20ppm is good and you get that from fish waste, then you likely are fine, I'd leave it be. 10-30ppm is a decent range, but this assumes the readings are ACCURATE from the test kit, which IME, it is rarely the case.

To check this, since you are basing all of your management decision on this one "guess", I'd run some standard known solutions to verify the NO3 test kit. If not, you CANNOT say what the NO3 is or is not.

See LeftC post on how to make a reference solution for NO3 and PO4.
It's not hard and save the solutions in some small bottles for future use.

IME, CO2 is by far more of an issue, much more toxic than ANY nutrients, kills/stresses more fish than any other planted tank parameter. 45 ppm is about the limit for discus with the best equipment and conditions I could provide.

They start to turn dark and change behavior, like NO3, the CO2 is calibrated method using this method for measure. Below this, they breed and have excellent color.

I'd worry more about the CO2, you cannot kill them with KNO3 unless went insane with the dosing and stopped doing water changes for a month or something.

It took over 160-200ppm of NO3 from KNO3 to kill Amano shrimp and that was for a LD50 over 3 days. Warm water fish are much less susceptible NO3 than cold water fish in general also. Large fish and warm temps = low O2, so make sure there's good current and O2 for discus. They can hide or move where there is less flow and a little exercise is not bad for them, makes them eat better.

Regards,
Tom Barr
 
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