# NO3 to PO4



## andy485 (Aug 19, 2005)

I am trying to figure out a dosing schedule for myself and need to see if some of you think this will work. My tank is well established with medium algae growth which my flag fish are taking care of on everything but my micro sword which is covered pretty good with BBA I think. My specs are below. 

In a whole week if I dose a total of 32ppm NO3 and 4.9ppm PO4 am I inviting more problems?

You see the trouble is I have some green spot algae and have read that uping the PO4 will help this but I have also read that NO3 to PO4 should be 10 to 1. So does that mean I need to raise NO3 to 50? I have fish in this tank also and I am afraid to raise NO3 levels that high.


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## djlen (Jun 22, 2004)

IMO both of those numbers are a bit too high. 10:1 is correct, but I'd shoot more for 20-25ppm/N: 2.5ppm/P.
How heavy is your plant mass and what plants?
How many and what type fish do you have in your tank? With a light fish load you can go a bit heavier on the KNO3 to add a bit extra K without stressing fish. If you have a heavier fish load, you might consider some K+ for the plants.
You don't mention traces. They are necessary for balance.
What is the wattage and type light you are supplying over the tank? 

Len


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## Laith (Sep 4, 2004)

andy485 said:


> ...
> In a whole week if I dose a total of 32ppm NO3 and 4.9ppm PO4 am I inviting more problems?
> ...


If I understand correctly, this is the total amount *dosed* per week and not the levels you are aiming for in the tank? If that's the case then you should be ok with this amount of dosing (I normally dose around 4mg/l of NO3 per day and 0.9-1mg/l per day of PO4), assuming that you have good lighting (more than 2wpg), adequate CO2 and *lots* of plant mass. If any of these three are not up to par then dosing as much as you are is not going to help.

Before increasing the NO3 dosing to 50ppm per week I'd make sure your CO2 is good. BBA is usually a sign of low CO2, given that the other elements are in adequate supply. Don't worry too much about the ratio.


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## aquabillpers (Apr 13, 2006)

There can be a difference between what you are dosing and what is in the water column.

I would get inexpensive nitrate and phosphate test kits and see what is actually in there. I use API; there are others. Shoot for an 8:1 to 12:1 N to P ratio and dose accordingly. 

There is no need to guess. Most of the inexpensive kits are accurate enough at the low end for normal aquarium needs.

Bill


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## Laith (Sep 4, 2004)

Sorry, maybe I wasn't clear enough in my post. The fertilizing method I was referring to with that type of dosing is the Estimative Index method where you just make sure you have enough of all plant nutrients and do 50% weekly water changes to take care of any excess buildups.

This method does not require dosing to specific tested parameters... in fact there is little need to test. The method that is more suited to dosing to specific tested parameters would be the PPS method (search here for that method).



> There is no need to guess. Most of the inexpensive kits are accurate enough at the low end for normal aquarium needs.


I tend to disagree with this statement. Blindly trusting inexpensive kits *will* lead you to trouble. If you do want to test, calibrate/test your test kit with a known concentration to make sure the kit is giving you correct numbers. I've seen all types of Nitrate and Phosphate test kits test positive even with distilled water and test negative with massive amounts of the target chemical present...  But if you calibrate, then you can have more confidence in the kits...


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## aquabillpers (Apr 13, 2006)

Hi!



Bill said:


> There is no need to guess. Most of the inexpensive kits are accurate enough at the low end for normal aquarium needs.





Laith said:


> I tend to disagree with this statement. Blindly trusting inexpensive kits *will* lead you to trouble. If you do want to test, calibrate/test your test kit with a known concentration to make sure the kit is giving you correct numbers. I've seen all types of Nitrate and Phosphate test kits test positive even with distilled water and test negative with massive amounts of the target chemical present...  But if you calibrate, then you can have more confidence in the kits...


I think that "blindly" doing anything will lead one to trouble. But if one thinks that he is dosing properly and his plants still aren't doing well, maybe what he thinks he is dosing really isn't what the plants are getting. Several things could cause that: measurement errors, chemicals in the source water, faster or slower growth of the plants, substrate leaching, the amount of fish food, and so forth.

The test kits that I use (infrequently, I might add) are consistent from test to test and are sufficiently accurate at low PPM levels. If phosphates consistently test at 1.0 PPM they might really be 0.8 or 1.2, but if one day a test shows them at 0.1, I know that I have a problem.

If Andy doesn't inject CO2 he should avoid frequent water changes, because these add a jolt of CO2. The slow-growing plants can't make use of that, but the algae can. (Per Tom Barr.) Here's a link: http://www.barrreport.com/forums/showthread.php?t=2599&highlight=water+change

Bill


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## Lord Nibbler (Dec 22, 2005)

I have a question about phosphates:

My tap water is very high in phosphate (around 3ppm to way above the scale). This, unbelievably, is accurate for the tap water in the area. Should I worry about trying to remove phosphate from my aquarium water or just be happy that its there and add nitrogen?


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## hoppycalif (Apr 7, 2005)

3 ppm of phosphate is not excessive, so don't try removing it. But, also don't expect that amount to still be there a week later, after the plants have been using it. I would still dose phosphate, but at a lower amount per dose, just to be sure there is always some available. Remember, fertilizing is not a matter of measuring what is in the water and assuming that amount will always be in the water. We want it in the water because plants eat it, so if we don't dose, the amount in the water drops, and it can drop rapidly. Also, just because your test kit says you have 3 ppm doesn't mean you do. It is very hard to measure such a low amount accurately. This doesn't mean possible 10% errors, but possible 100% errors.


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## Lord Nibbler (Dec 22, 2005)

Actually I don't dose phosphate, it comes out of the tap at that concentration!


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## hoppycalif (Apr 7, 2005)

Lord Nibbler said:


> Actually I don't dose phosphate, it comes out of the tap at that concentration!


Yes, I understood that. But, my comment is still valid. If you put water having 3 ppm of phosphate in a tank of actively growing plants, it will only take a few days at most for them to use up that phosphate, so you need to add phosphate every other day or so to maintain an adequate level in the water. You could do this by changing a third or so of the water every other day, but it is a lot easier to dose KH2PO4.


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## aquabillpers (Apr 13, 2006)

hoppycalif said:


> 3 ppm of phosphate is not excessive, so don't try removing it. But, also don't expect that amount to still be there a week later, after the plants have been using it. I would still dose phosphate, but at a lower amount per dose, just to be sure there is always some available. Remember, fertilizing is not a matter of measuring what is in the water and assuming that amount will always be in the water. We want it in the water because plants eat it, so if we don't dose, the amount in the water drops, and it can drop rapidly. Also, just because your test kit says you have 3 ppm doesn't mean you do. It is very hard to measure such a low amount accurately. This doesn't mean possible 10% errors, but possible 100% errors.


I maintain 3 soil based tanks. All use the same substrate and the same water source, and all have a fairly large fish population. All, knock on wood, have very good plant growth. All have about 2 wpg and no CO2 augmentation.

Two of the three have maintained phosphate levels at between 2 and 3 ppm for the last 12 months, without any additional dosing. Each has required additional nitrates every 2 or 3 months in that period, a total of 1/4 to 1/2 tsp.

The third does require a few drops of Fleet Enema every 6 months or so to keep the phosphate level at around 1 ppm. It also requires nitrates every now and then.

The test kit that measures 3 ppm in 2 tanks also measures 1 ppm or less in the third, consistently.

Plants in high light/high CO2 environments use more nutrients than do plants in low light, low CO2 tanks.

BTW, probably of greater importance is the ratio of nitrates to phosphates. It should be about 10 to 1, give or take a little. 3 PPM of phosphates is OK, but the nitrates should then be about 30 PPM.

Bill


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