[RisingSun]

I just tested my tank and I have about 15ppm of nitrate, and 1ppm of phosphate. I dose phosphates and potassium, but I've never dosed nitrate. Is there any reason to dose nitrate if my fish waste keeps it at 15ppm already? Is the nitrate from the salt any more "preferred" by the plants? thanks!

 

[Raymond S.]

Nitrate is coming from the NO3 in KNO3 ?
How/what are you using to dose Potassium ?

 

[RisingSun]

I'm using KSO4 and KH2PO4 to dose potassium. I'm not currently using KNO3, all my nitrate is coming from waste. I'm wondering if I need to start dosing KNO3 if my nitrate is already so high, or if I can just continue not dosing nitrate.

 

[Raymond S.]

I use 1/32+1/16 tsp K2SO4 and 1/32 KNO3 to equal the 1/8 tsp that the calculator says is one dose of EI level for my 10g tank. I only have two Neon size fish in there but many snails. I get about a 15 on my test. Hard to be exact with color shades. When I use them 50/50 I get a much darker Orange on the test.
There is very little K in KH2PO4 so it shouldn't be counted, not so much for the percent in KH2PO4, but for the amount of KH2PO4 that is used.
If you aren't having any problems/w growth that may indicate a need for more nitrates, then I would just keep using the K2SO4. The suggested amount of nitrates for a planted tank are anywhere from 5-30ppm. 15 I would think is easier on the fish.

 

[imcmaster]

Is there any reason to dose nitrate if my fish waste keeps it at 15ppm already? Is the nitrate from the salt any more "preferred" by the plants?

Whether bacteria oxidizes NO2 to NO3, or KNO3 disassociates to NO3, the end result is the exact same compound. As Raymond suggested, there is no reason to add more (in the form of KNO3) given your rather lean dosing approach unless your plant uptake starts to exceed the rate of nitrogen production by the fish.

 

[mattinmd]

I'm using KSO4 and KH2PO4 to dose potassium. I'm not currently using KNO3, all my nitrate is coming from waste. I'm wondering if I need to start dosing KNO3 if my nitrate is already so high, or if I can just continue not dosing nitrate.

First, are you sure you are at 15ppm? Have you calibrated your test? Be aware nitrate tests are notoriously inaccurate in terms of scale. My API nitrate test repeatably reads 6x the actual concentration of NO3.

That said, if you are at 15ppm, you don't need to add KNO3, as long as you are keeping up your K with K2SO4... I use a half-dose KNO3 modified EI low-light dosing strategy, making up the rest of the K with K2SO. I have livebearers, so I'm a bit overstocked and don't need to dose as much KNO3 to get to my target nitrate levels.

Also, the term "so high" to refer to 15ppm of NO3 does raise my eyebrows.. 15ppm is not high in my mind.. 10-20ppm is what I'd consider a normal level for a planted tank, and you're perfectly in the middle of normal.

 

[RisingSun]

First, are you sure you are at 15ppm? Have you calibrated your test? Be aware nitrate tests are notoriously inaccurate in terms of scale. My API nitrate test repeatably reads 6x the actual concentration of NO3.

That said, if you are at 15ppm, you don't need to add KNO3, as long as you are keeping up your K with K2SO4... I use a half-dose KNO3 modified EI low-light dosing strategy, making up the rest of the K with K2SO. I have livebearers, so I'm a bit overstocked and don't need to dose as much KNO3 to get to my target nitrate levels.

Also, the term "so high" to refer to 15ppm of NO3 does raise my eyebrows.. 15ppm is not high in my mind.. 10-20ppm is what I'd consider a normal level for a planted tank, and you're perfectly in the middle of normal.

I also use the API Nitrate test, and compare the results to http://imageshack.us/scaled/large/11/ahwm.jpg. You bring up a good point that the test might be poorly calibrated. Is there any way to test the calibration without having any KNO3 on hand? Thanks!

Edit: I have a jug of distilled water. Can I use that to sanity check my nitrate test by making sure it reads 0 nitrates?

 

[greaser84]

I also use the API Nitrate test, and compare the results to http://imageshack.us/scaled/large/11/ahwm.jpg. You bring up a good point that the test might be poorly calibrated. Is there any way to test the calibration without having any KNO3 on hand? Thanks!

Edit: I have a jug of distilled water. Can I use that to sanity check my nitrate test by making sure it reads 0 nitrates?

No you'll need KNO3 to calibrate. When you get some do this.... http://www.plantedtank.net/forums/showthread.php?t=83545#post800612

 

[mattinmd]

+1.. my test reads 6x normal, but it does correctly zero...

My first major clue that it was out-of-calibration was when it told me my munincipal water supply had almost 20ppm of Nitrate in it..

If you have trustworthy nitrate level reports for your tap water, you can use this as a rough check. If it tells you something absurd for that, odds are it is off..

However, from there you really need calibration solutions made with distilled water and KNO3.

 

[Diana]

If you do find that you have enough nitrogen from fish food, then the fish food is probably also supplying a fair amount of phosphorus. Have you run your dosing of phosphorus through a calculator? Did the results make sense?

Generally, if there is enough nitrogen from fish food, then there is also enough phosphorus and most traces.
Fish food is low in potassium and iron.
It is also low in calcium but water changes usually deal with that, as long as the GH is over 3 degrees.