Adding Potassium Nitrate when There's Nitrate in the Water

[DTs]

This is probably a dumb question, but if I have nitrate readings of about 2-5 ppm, should I still add potassium nitrate regularly to the water?

I would assume I shouldn't since nitrate is already in the water, but you never know.

I do 50% weekly water changes, use halide lighting, and have extremely fast growing plants due to pressurized CO2 supplementation.

 

[Tempest]

You will probably want to keep an eye on it with a test kit for a while. That wouldn't be enough to last mine a week. Sometimes our water has up to 10ppm but I still need to supplement by the middle of the week.

 

[Slappy*McFish]

Potassium Nitrate (KNO3), is a better source of nitrate than it is potassium. (10ppm of KNO3 = about 6ppm of NO3 and 4ppm of K.) Don't rely on it as your only source of potassium. You want to dose 10-20ppm of K per week.

Potassium Sulphate (K2SO4), should be used in conjunction with KNO3. Just dose enough KNO3 weekly to achieve about 6-10ppm of nitrate, and add K2SO4 to make up the remaining ppm needed to reach your target level of K.

 

[plantbrain]

I've figured that unless you have 4x the need for N that you do for same amount of K, you will not need any K2SO4 really.

If the tap was higher, say 20-40ppm of NO3, then niot using the KNO3 and using the K2SO4 would be good.

But except in a few cases where the folk's have high NO3 int he tap or too many fish/fwew plants, not enough plant uptake of NO3, most will be fine using KNO3 alone.

It will not hurt adding more K+, although some have reported issues with some picky plants, I cannot confirms this as of yet and the jury is still out about why. But you do not need so much much K+ in any event. It's unlikley folks wil have a K+ limited tank using KNO3.

At 2-5ppm of NO3, I doubt they will need to worry about getting enough K from KNO3.

Regards,
Tom Barr

 

[Slappy*McFish]

I stand corrected, I suppose...or those figures aren't as important as I had thought.
I used the 'Estimative Index' and Chuck's Aquarium Calulator as a rough guide to get these figures. Does he still need to target 10-20ppm of K? and will the KNO3 help him reach that target (if necessary) without adding too much nitrate in the process? Or does it even matter what his nitrate(ppm) is? I assume you want it to be <=10ppm or within a reasonable level, of course.

..and ofcourse this is based on my assumption that he was adding KNO3 as a source of K as opposed to a source of NO3 only.

 

[plantbrain]

Well relative to Nitrogen, you need about 4x less K before it'll become limiting.
Since KNO3 has ~60% NO3 and ~40% K+, we are not really close to that.

I've suggested this change since it's one less thing to dose(the main reason) and some folks have claimed, that high K+ is causing them Ca like deficiencies in about 3 species of more ecclectic plants, something I have not been able to reproduce yet in my tanks at home using K2SO4.

They claim 20-30ppm causes the issue, most of the advice I give sits about 10-20ppm of K per week so that's enough, maybe even a little less.

There's no reason to add more than that, but the older 20-30ppm is just wasteful, even if there's no issues with high K+ causing stunted new growth.

I've kept plants for years at 30-50ppm K+ and never saw anything. Close to 200 ssp also.

I'm still looking into their problem though.

Regards,
Tom Barr

 

[Slappy*McFish]

Thanks Tom, I just now noticed your sticky at the top of the page on this matter. :argh

 

[plantbrain]

:argh
I have had more trouble figuring out why the people have Ca like deficicencies though and why I don't, but at least the "how" is now better applied even if the why is always much more difficult to answer.

It moves us towards a simpler dosing routine which I am still moving towards.
I'm trying to come up with a suitable matrix for NPK for a substrate unlike Jobes sticks which have NH4/Urea. Some NPK to the substrate would help a little if you really kept up on the macro's in the water column, but adding a bit more to the substrate in the right form will alllow some with less light to fertilize less, not worry if they skip a dosing etc.

All plant tanks get some nutrients from both places to varying degrees. Adding a little bit more to the substrate upon set up will get things rolling a little better. I've and many other 's have suggested this over the years, but until I found out it was NH4/Urea that caused the algae, folks were leary of richer substrates.
Deleting this, we can do this well if the nutrients dissolve slowly(10-6 months, perhaps a year in some sort of matrix that dissolves at a fairly constant rate.
Agar, gelatin dissolves too fast and seems to be too porous for small nutrients like NO3 etc.

But ideally, it would be fun to dose weekly with low to moderate light, and perhaps add some NPK/traces with higher light without depending quite so much on the water column but the water column will not mistreat you if you add the nutrients at regular intervals.

I do not think you will grow nicer plants by adding more NPK in the substrate, but it might make your rotuine a little easier and have a little back up of nutrients in case of neglect......something we all do at some point.


Regards,
Tom Barr

 

[nfinit1]

Nitrates at 12.5 with Tetra test kit

Sounds like I came in on this at the right time

A 20% to 25% water change was done to 75 gal planted tank with 1.73 watts per gal Sunday.
Seachems Flourish products were added
Excel(CO2),Iron, N, K, P, and Trace
Since then I add Excel Co2 Everyday

Testing today...Ammonia Ok, Nitrites OK, Nitrates are 12.5

What can I do to bring it down or should I just add Phosphous to help the plants bring it down naturally??/ (I am correct right)

My fish load is
9 celebs rainbows
8 neons
7 flame tetras
4 otos
4 green corys
2 dorio botias

My plants are
3 swords
Sag
dwarf Sag
5 Anubas
3 to 4 crypt wenditii
3 crypt balansae
3 crypt retrospiralis
hygro tropical sunset about 7 to 8 stems
telanthera rosefelia
Something like the telanthera
Rotala Indica
microswords

Help!!!!!!

 

[Slappy*McFish]

What's the NO3 level of your tapwater? Though, I don't really see a NO3 reading of 12.5 as something to be concerned about. Doing another water change should bring it down further if that is your goal. This is assuming your tap has a NO3 reading less than 12.5.