# Nitrate to phosphate ratio



## GulfCoastAquarian (Jul 30, 2002)

That is correct. To help prevent algae, and encourage optimal plant growth, your Nitrates should be 10x higher than Phosphate levels. Of course, this is within reason - if your Phosphates (PO4) are higher than your Nitrates, it is possible that your PO4 levels are entirely too high. If they're much higher than 1.0ppm, I would reduce their levels through water changes and bring your Nitrates up to 10ppm by adding KNO3 (Stump Remover - Potassium Nitrate).


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## malkore (Nov 3, 2003)

Basically, you want phosphates at 1-1.5ppm max. this puts your desired nitrate at 10-15ppm. A tank tears through nitrates more quickly than phosphates, so some of us like to keep nitrates at 20ppm, and phosphates no higher than 1.5ppm. I started doing this, and saw noticably better plant growth in all plants.


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## matpat (Jan 22, 2004)

If I remember correctly, what we are looking for is a N : P ratio of 10:1. This would actually be Nitrogenhosphorous not Nitratehosphate. 

10ppm NO3 : 1ppm PO4 would actually be:

2.27 ppm N : 0.33 ppm P or close to a 7:1 ratio.

Maybe a 16:1 ratio of NO3O4 is what we should be looking for (3.63 ppm N : 0.33 ppm P).

I have been dosing 8ppm KNO3 (1/2tsp KNO3), .46ppm PO4 (1ml fleet) three times a week for the last two weeks. My NO3 has remained stable at 2ppm and phosphates have been .1 No algae so far and the tank is crystal clear. 

Does it really matter what the ratio is as long as the plants are doing well and the algae is not?


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## Splash (Feb 18, 2004)

:? Hmmm. I'm not sure if this is correct, but I thought that the 10ppm NO3 : 1ppm PO4 was based on the Redfield Ratio for aerobic decomposition of simple sugars: 106 C:263 H:110 O:16 N:1 P, which are all in moles. (Chemical "moles," not the little furry ones!) 

So that also means 16 moles of NO3 to 1 mole of PO4. The atomic mass of N is 14.007 g/mole, P is 30.974 g/mole and O is 15.999 g/mole. So a 16N:1P ratio in moles translates to 992064 mg NO3 : 94970 mg PO4. Dissolve both the NO3 and PO4 in one liter of water and simplify the ratio gives approximately 10 ppm NO3 : 1 ppm PO4.

So, _VOILA_! My solution might be totally hosed, but I get the correct number!!!  




matpat said:


> If I remember correctly, what we are looking for is a N : P ratio of 10:1. This would actually be Nitrogenhosphorous not Nitratehosphate.
> 
> 10ppm NO3 : 1ppm PO4 would actually be:
> 
> ...


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## fishlady (Jan 12, 2004)

Splash: You are way over my head with that last answer. Just learning about plants and levels. etc! :?


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## Splash (Feb 18, 2004)

Sorry! The simple (simpler?) answer is that the composition of plant matter has an average ratio of nitrogen to phosphorous _atoms_ (not ppm) of 16 N for every 1 P. We, therefore, assume that if we provide dissolved nitrogen and dissolved phosphorous as fertilizer in a similar ratio, the plants will be able to use both nutrients most effectively. But we don't fertilize with pure N & P atoms, we use nitrate (NO3-) and phosphate (PO4+). So we have to correct the atomic ratio of 16 N: 1 P to a mass-based (or "weight-based," if you prefer) ratio, plus we must account for the mass of the extra oxygen atoms (O) in the nitrate and phosphate salts. When you do that, you get a corrected ratio of about 10 ppm nitrate: 1 ppm phosphate.

Simplest answer: Keep your phosphate low...less than 1 ppm. Add nitrate as necessary to get a ratio of ~ 10:1 for ppm nitrate to ppm phosphate.

In my system, my plants tend to use up all of the nitrate, but there is still plenty (~ 1 ppm) of phosphate remaining. That is a recipe for disaster. The plants slow or even stop growing because the nitrates are too low, the excess phosphate can promote the growth of hair and brush algae, and if the nitrate gets extremely low it might stimulate a very messy growth of cyanobacteria (aka "blue-green algae"). So I add additional nitrate to the tank until I get 10 ppm Nitrate to balance my 1 ppm phosphate. By doing so, my plants will continue to grow and suck up the excess phosphate.

Hope that helped!  




fishlady said:


> Splash: You are way over my head with that last answer. Just learning about plants and levels. etc! :?


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## matpat (Jan 22, 2004)

Fishlady, she's way over my head too! All I was getting at was does the ratio matter if the plants are doing well and the algae isnt. Mine are, and I suppose the others are too, even though we use different methods of dosing.

However, I found it to be a job trying to get my nitrates and phosphates to be at the 10:1 ratio. All it gave me was green water and worries. I didn't start this to turn it into a job, I just wanted to have fun and grow plants. After battling green water for a couple of weeks, I did a lot of reading, I took someone's advice, and started a simple dosing routine which gave me some good results. No more green water, no more headaches, and the enjoyment of looking at a pretty tank.


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## Rolo (Dec 10, 2003)

Matpat, your 7:1, Nitrogen is kinda flawed. As splash commented its based on the mole. Don't worry Splash, I totally understand where your coming from!

Maybe your green water problem most likely wasn't the ratio - for instance there is a certain max amount of P you should have like 1ppm...over that is getting to be too excessive and a proper ratio won't fix things. Also you've got to make sure your plants can use the NO3- and P, meaning your K, traces, Fe, light, CO2 all need to be adequate...if one is too low, then that will limit your plants ability to compete with algae.


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## matpat (Jan 22, 2004)

My greenwater began shortly after I tried to get my NO3O4 in balance. I began dosing 5ppm KNO3 and 1ml Fleets (.46ppm) however, I couldn't keep the NO3 in the tank, It was zero each day of testing. Test kit was OK, KNO3 was OK. Plants were using NO3, too fast. Still are. I now dose 1/2tsp KNO3 every other day and get a reading of 2ppm the next day. I dose phosphates (1ml fleets/0.46ppm) when they drop to 0.1ppm. They usually read 0.1ppm the next day. They have yet to be above 0.2ppm. These are dosed with Iron (based on the tips of Mayaca getting light) 15 ml of Flourish trace and 5ml of flourish. 

Whatever the reason, the tank is fine now, maybe it won't be in a few weeks. Time will tell. However, I do not have the knowledge base to discuss moles and atomic ratios.  

I want my planted tank to be fun. I do not want to work all the time trying to maintain a 10:1 ratio in my tank. A day after dosing I have 2ppm NO3 and 0.1 ppm PO4 and it seems to be working. Maybe I should be looking at how much the plants consume versus what's left over in my water column?

Fishlady,

I apologize that my comments have completely hijacked your thread and probably even caused you more confusion. It was not my intent.


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## fishlady (Jan 12, 2004)

No problem matpat, I find it all interesting but very confusing. My problem is the high phosphate comes from having well water and I worry about adding nitrate because I have angels and I read that they dont do well in water with nitrates. Comment?? Thanks-


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## Wö£fëñxXx (Dec 2, 2003)

Happy plants=happy fish  

I have 3 large angels in my 46 I dose KN03 daily, they love it..LOL really

10:1 ratio N03/P04


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## Splash (Feb 18, 2004)

Yeah, my municipal water comes out of the tap at 1 ppm PO4, so water changes are like adding fertilizer....What's a fella to do?

IMO, 10 ppm NO3 won't bother your angels. I had angels (big, messy fish!) in my unplanted first tank, which often had nitrates of 20 - 60 ppm. I wouldn't recommend levels that high, in general. It's bad for inverts like shrimp, not great for plants, and might increase fish stress some. You wouldn't know it by looking at my angels, however. They were strong, happy, greedy little cichlids and grew like weeds...or, maybe, like algae. 




fishlady said:


> No problem matpat, I find it all interesting but very confusing. My problem is the high phosphate comes from having well water and I worry about adding nitrate because I have angels and I read that they dont do well in water with nitrates. Comment?? Thanks-


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## Mini4x (Feb 3, 2004)

Can someone clarify the Fleet's and Stump Killer info for me?


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## matpat (Jan 22, 2004)

Fishlady,

If you do begin to add nitrates to your tank, do it slowly so the fish can acclimate themselves to the change. 

Mini4x,

Fleets Enema (Monobasic Sodium Phosphate and Dibasic Sodium Phosphate) is used to treat constipation. You can buy it at most drugstores. I got a 2 pack at WalMart (2 were cheaper than one) for about $2. Here is the info I have on dosing Fleets:

1ml of fleets added to 100L will raise the PO4 by 1.33ppm. 

Stump Remover is Potassium Nitrate. Spectracide brand is *supposed* to be 100% KNO3. I do not know about other brands. I dose about 9 grams a week of KNO3 for my 75g tank. If you want to be sure, get the MSDS sheet for the brand you want to try.

There are many places to buy KNO3 (Potassium Nitrate) and KH2PO4 (Potasium Phosphate) online. wwwdot gregwatsondotcom is a good place to start your search. Hope this helps.


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