# Increasing P+ K to lower N?



## xev11 (Feb 18, 2010)

I have very high nitrates (even after WCs). If I want to increase the level of P + K to help promote plant growth and hopefully decrease the nitrates, how do I figure out the safe levels of each that I can dose?

Should I just follow the PPS Pro or EI dosing method for a month or so and hope the rate of plant use is greater than the rate of nitrate production? Or can I dose higher amounts of P + K initially so the nitrates are used quickly from the beginning? To this I would also need to know the potential levels of toxicity to fish and plants. 

Note: I am already doing other things in hopes of reducing nitrates (WCs, substrate cleaning)


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## niko (Jan 28, 2004)

By starting both PPS and EI you are throwing your tank into a completely different mode. It may work or it may not work. If it doesn't work the problems are BIG. It all happens very fast. Even if things work you will be forced to maintain the tank without a choice. If you miss a week or two of water changes there will be big problems again. That's the reality of adding ferts to the water. No one wants to openly talk about that but you can try and see what you experience.

A better approach is to start adding small amounts of the ferts. One at a time. Start with K, then Ca, and Mg (if hardness is low or if Ca or Mg is needed), then traces, then Fe. Only after that start adding N. Phosphate is last. Usually fish provide enough Phosphate.

And before starting any additions of chemicals make sure your filter is good - size and media. Also the water flow needs to be such that all plants gently move in the current.


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## xev11 (Feb 18, 2010)

I didn't mean PPS and EI simultaneously, just that i would follow one or the other. 
Since I plan on doing ~30% WCs weekly (or more frequently) I could make sense (to me) do follow EI, but would the extra ferts lead to a fast absorption rate? Or do plants have a set rate that they process at when the ferts + light are available?

I don't want to do wild experiments since this is my main tank. The only issue is the high N and organics. (I have been reading the organics/BBA thread and understand there is some sort of relationship there).

I have a AC 20 + Air sponge filter. I'll be changing the 20 to a 30 this week. If nothing is blocking the outflow then there appears to be enough flow throughout the tank. 
[I have filter floss in the outflow currently to trap any small particles that aren't caught in the internal sponge -- to help reduce organics/stuff floating around]


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## micheljq (Mar 25, 2013)

You can try only adding K for beginning.

I don't agree that fish always provide enough P though, depends on light, CO2 and probably other conditions. 

Michel.


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## xev11 (Feb 18, 2010)

No co2. Only excel every several days. Light is a planted+ led. On for about 7hrs. Duration Was reduced to try to curb bba.


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## Zapins (Jul 28, 2004)

Plants will only take up as much of each nutrient as they want unless they are limited. So if a plant needs 5 ppm nitrate, 1 ppm phosphate and 4 ppm K a week and you give them 50, 10 and 50 ppm they will still only use up 5, 1, and 4.

If on the other hand the plant is not getting its minimum values then adding the missing element will help it grow faster which may cause it to use more of the other nutrients. This is because plants only grow as fast as the limiting nutrient. And once all nutrients are provided in unlimited quantities then the plant will max its growth rate out and not be able to take up more than that.

This depends mainly on lighting intensity, but also on temperature, and CO2 availability.

If you want to reduce your nitrogen levels then water changes are the way to go.

Toxicity levels for NPK are fairly high and aren't known with great specificity. I wouldn't dose more than 50 ppm nitrate, 4 ppm PO4 and maybe 150 ppm K. Usual recommended levels are around 15 ppm nitrate, 2 ppm PO4, and maybe 30-50 K. You can use the fertilator or calc.petalphile to calculate what you should add.

http://www.aquaticplantcentral.com/forumapc/fertilator.php

http://calc.petalphile.com/


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## old 97 (Jul 25, 2011)

xev11 said:


> I have very high nitrates (even after WCs))


If you change 50% of the water and the Nitrates are not reduced by @ least 50%, more water changes ( from the same source) will not help.


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## Zapins (Jul 28, 2004)

What are your nitrate levels?


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## xev11 (Feb 18, 2010)

I have the API liquid test so the results may not be totally correct (compared to Sera). I will post images later but from my memory before my last WC they were around 160, after the 30-40% WC somewhere around 120. 

It's very hard for me to do larger volumes as I have a breeder net with some small rasboras + shrimp that would be above the water line for big volume extractions. 

I do understand that such levels should theoretically be harmful to the fish in the long term


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## old 97 (Jul 25, 2011)

Perhaps test the source/tap water. Double check your test validity against a bottle of Evian; or the like.


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## xev11 (Feb 18, 2010)

I checked my tap and its pretty much 0 nitrates. I also did a 25%tank/75% tap nitrate test a week ago, and the color was only slightly lighter than all tank. (Deep red).


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## xev11 (Feb 18, 2010)

Atchmnt 1: After most recent 30-40% WC








Atchmnt 2: 25% tank with 75% tap. (tube on left) 100% tank (tube on right)


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## Zapins (Jul 28, 2004)

I'd just do several large water changes as difficult as they may be. Once you get the nitrates out they are unlikely to come back unless something is decaying in the tank.

Do you use soil or aquasoil?


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## xev11 (Feb 18, 2010)

Eco complete. A while back I put chunks of dry soil in the center which may be causing the issues now. I'll proceed with water changes and add more plants and follow the calculated dosing.


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## Zapins (Jul 28, 2004)

Sounds like a solid plan, be sure to update us on what happens! Pics would be nice too.


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## xev11 (Feb 18, 2010)

Cool. Appreciate the help. I'll do that


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## niko (Jan 28, 2004)

I meant using either PPS or EI. Keep in mind that PPS is a scaled down variety of EI. Either approach will push you into an endless chase of constantly missing ferilizers. If all goes well you will never be prepared to solve problems. You will always end up doing more of the same - ferts juggling and water changes.

Note that in an aquarium there are the basic processes that must work properly BEFORE the secondary stuff can do its thing. Flow and biofiltration are primary, ferts are secondary. Try ferts before flow/biofiltration are established properly and you will have problems. EI and PPS make you believe ferts are everything. If your tank does not work after playing with wc and ferts then you are left with no answers. And yes - the maintenance is mandatory weekly chore with EI and PPS. That is because you are keeping the tank looking good and not letting it help you stay hands off.

Try EI and see for yourself if you like it.


Sent from my RM-893_nam_att_206 using Tapatalk


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## Diana K (Dec 20, 2007)

Reducing the amount of nitrogen entering the tank would be high on the list of things to do, also. 
Feed the fish WAY less. 
Perhaps only one meal every 2-3 days, and only half as much as you had been feeding. 
Do not do this if you have predators, though. You can try cutting down their food, but not to the point that they eat each other. 

If the new (tap) water has 0 nitrates, but has some ammonia (ie: chloramine) then that is still a source of nitrate. Nitrifying bacteria will deal with the ammonia and it will end up as nitrate. Still, a lot less than is in the tank, now. My tap water tests 1 ppm ammonia (from chloramine). 

Move the fish trap into a bucket long enough to do larger water changes. Or move these fish to a separate tank. Set up a system where you do a 'constant in/constant out' sort of water change. Make up a big supply of good water (correct temperature, mineral levels, dechlor) and start pumping it in slowly while you are also draining the tank. Concentrate on draining away from the incoming water. For example, drain from near the substrate, picking up fish waste and so on while the incoming water is sheeted across the top of the tank. 

Someone has done the math on this sort of water change, and I think it works out to about half as effective as doing a 'water out followed by water in' sort of water change. 
Example:
A 100 gallon tank, set up 50 gallons on new water. 
~Do a 'constant change' sort of water change and you get the results of about a 25% water change. But the change is less stressful also because the water level is only allowed to drop a couple of inches. Just enough to be sure the tank won't overflow. 
~Do a 'water out/water in' type of change and that is a 50% water change. 

I have noticed that even when I do the math, and really do a 50% water change the NO3 level does not always drop as much as I expect (50%). I suspect there are some reserves of NO3, perhaps in the substrate, that enter the water after the water change. This is why as thorough a gravel vac as possible can help. Can't really do that when the plants are rooted all over, but when the tank is not fully planted you can dig in a bit deeper where the roots are not, and you can siphon debris that is caught in the leaves and stems deeper in the tank. 

I have a hard time reading the colors beyond 40 ppm. To me, they are all the same shade of deep pink, and signal trouble. When I see that deep color I will set up for water changes, a few big ones, or lots of little ones, and keep at it until the test is readable (ie, about 20 ppm or less)
If the real NO3 level was 80 ppm, and I did a 50% water change, the test ought to read 40 ppm. But since that still looks like the higher numbers, it is not enough water change, no matter what the real value is. 

However, your initial question is valid: If you improve conditions for the plants then they ought to help with N removal. 
Light. 
Carbon, potassium and iron. 
After these, the other nutrients. As suggested above, try them one at a time and see if you start seeing results. 

Low tech tanks are often lacking C, K and Fe. When these needs are addressed, then the other nutrients might also be lacking, as the plants get more active. 

More plants, especially plants with roots in the water and leaves in the air. These plants get their carbon from the CO2 in the air, so are able to grow faster and therefore use more N than plants that grow fully under water.


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## Zapins (Jul 28, 2004)

Great info Diana.



Diana K said:


> However, your initial question is valid: If you improve conditions for the plants then they ought to help with N removal.


I'd like to add for perspective that in my 90g high tech tank with extremely high plant density the plants only use about 20 ppm of KNO3 per week. So even with unlimiting conditions and an extremely high plant mass they don't take up that much nitrogen.


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## xev11 (Feb 18, 2010)

Zapins said:


> Great info Diana.
> 
> I'd like to add for perspective that in my 90g high tech tank with extremely high plant density the plants only use about 20 ppm of KNO3 per week. So even with unlimiting conditions and an extremely high plant mass they don't take up that much nitrogen.


That bit of info really means to me that the only way for me to deal with my nitrates are with water changes and less food/fish. I don't intent on making this a high tech tank, even if it was, it would take several months to lower the N level to reasonable levels. That's assuming that the existing fish population wasn't contributing any to the process.


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## Zapins (Jul 28, 2004)

I agree with your conclusion. Plants will help remove some nitrate but they certainly aren't the nitrate sponge we sometimes think they are.

Water changes and reducing food are they way to go.


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## Diana K (Dec 20, 2007)

In my best tanks (for N reduction) I have house plants (Syngonium and Epipremnum) growing out of the tank with leaves in the air. 
In my ponds I have lots of plants that utilize the CO2 from the air. 

I think the unlimited CO2 plays a part in improving N removal. 

However, I agree with Zapins and xev11, plants cannot be relied on to improve really high N levels. To really correct this situation water changes and reducing the amount of N being added to the tank is the best way to go.


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## Window7 (Feb 23, 2012)

Do 3 50% WC/day for the next 7 days. Or 8 20%


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