# Phosphate to Nitrate Ratio?



## LindaC (Nov 7, 2005)

Do you always have to dose nitrate and phosphate at a 10 to 1 ratio? I seem to be having a hard time getting my phosphates under control. I am currently dosing 2/8ths tsp of KNO3 with 1/8 tsp of K and I'm still getting green spot algae on my glass. If I dosed the same amount of nitrate and phosphate, would the plants still utilze the KNO3 the same way?


----------



## dennis (Mar 1, 2004)

No, and sort of. IMO, dosing at 10:1 or focusing on any arbitrary ratio serves no purpose. For all intents and purposes, the most NO3 your going to need is 1-2mg/l daily. I have a 29 similar to you, similar lighting (6hr midday burst) and good CO2 levels. Happy plants (more or less), happy fish. Lately, I have been doing a lot of tracking of nutrient levels in the aquarium while recording the amounts I add..... My setup uses .75-1mg/l NO3 daily (not counting any organic sources that I obviously cannot track) Basically, if I added 10mg/l of NO3 from KNO3, in 5 days I would test 5-6.25mg/l in the water.

PO4 can build up quite a bit with "typical" dosing. I have not spent a lot of time tracking this nutrient; however, 3-4mg/l added over the course of a week is sufficient (but probably way to much) to maintain any range of levels. At this time, my estimate would be that 0.25mg/l PO4 daily use may be reasonable.

So, what does this mean to me? I would "suggest" that with a moderate fish load, you add 1mg/l NO3 and 0.5-1mg/l PO4 every other day (3 times a week Dose micros after the water change and start macros on the day after wc). Dose Flourish at 1ml per gallon over the course of a week and additional Fe at half that rate. If you can, try and get your tank levels of NO3 down to about 10mg/l and start dosing like I "suggested". Watch your plants, observe your fish/shrimp and algae conditions. I would be willing to bet you have very high nitrate levels at the moment

Most importantly, don't take what I say as "the way" to do things. I am simply offering a general idea of things that currently work for me. Ultimately, you will need to adjust for what works best in your situation. Give any changes 2-3weeks to really see their effect. Plant can change and adapt over night but conditions often rapidly change then slowly go back to some mid-point. It takes several weeks generally to see the long term affects of any change.


----------



## dennis (Mar 1, 2004)

I just analyzed my PO4 levels and information... I looks like over a long term period (55 days), PO4 use is ~0.33 mg/l daily for my situation.


----------



## artemism3 (May 21, 2005)

Dennis,

quick question or 2...

Is mg/l the same as ppm?

Second question/observation...with that formula, your 29g uses 22-30ppm of NO3 daily? 

Just making sure!

Thanks!


----------



## Edward (May 25, 2004)

dennis said:


> I just analyzed my PO4 levels and information... It looks like over a long term period (55 days), PO4 use is ~0.33 mg/l daily for my situation.


Is this uptake rate at continuous PO4 presence in the water column? Than what this would apply to is that the rate includes a luxury uptake as well. Do you agree?


----------



## dennis (Mar 1, 2004)

Artemism3..... mg/l is the same as ppm. My tank uses about .8 mg/l NO3 daily and .33mg/l PO4 daily, as an average. I'm not sure how you got that high number but sorry if my post was worded confusingly. 

Edward, that uptake rate was calculated/observed in a situation with at least 2 mg/l in the water column. Using a speadsheet, it shows a range of PO4 levels in the water between 1.07 and 4.11mg/l at the end of a day. Obviously those numbers are not accurate reading but calculated "theoretical" numbers to help me consider the situation. PO4 levels in this tank had been in the 2-4mg/l range for 19 days prior to the period I calculated for the average. Also, I stand corrected (not that it actually matters) PO4 uptake for the 55 days was 0.345 daily and for the 19 days previous was .33 daily. I am not exactly sure what you mean my luxury uptake, but I would think that as the tank was saturated with PO4 prior to, and at the start of both average periods, that any luxury uptake would have happened before the period and would net be affecting the averages. Does that make sense?


----------



## Edward (May 25, 2004)

Dennis,
Thank you for sharing so detailed data. Good work. Sorry about asking unrelated question to this thread. It was related to our discussion the day before. 

Just a thought. If plants can live on 0.33 ppm PO4 a day and not depleting it, means they are running at luxury uptake rates. Plants take many times more mobile P then actually need to grow well. Question is, could these plants do as well on less PO4?


----------



## BryceM (Nov 6, 2005)

Linda,

In my tank I add NO3 and PO4 in a 2.5:1 ratio. I do a 20% WC three times per week (which is mathematically the same as a 50% change once per week). After each WC I add 4 ppm of NO3 and 1.5 ppm of PO4. Despite this, the actual water column levels end up around 10:1. How to explain this? I dunno. It's pretty clear that plants need and use much more nitrate than phosphate. Maybe it's explained by "extra" nitrogen entering the system via fish waste. Maybe the PO4 precipitates out of solution. Maybe my measurements are innacurate. Who knows. Dennis and I both use Lamotte kits for our numbers, but he's been more careful with his observations than me lately.


----------



## Edward (May 25, 2004)

guaiac_boy said:


> After each WC I add 4 ppm of NO3 and 1.5 ppm of PO4. Despite this, the actual water column levels end up around 10:1. How to explain this? I dunno.


True, this is because plants suck up PO4 much faster and much more of it then they actually need.


----------



## LindaC (Nov 7, 2005)

Thank you everyone for all your hope, I really appreciate it. I have one question and it may sound silly but calc was never one of my strong suits in school or college for that matter; I know that 5 mls equals about one teaspoon, so if I wanted to narrow that down to 1 ml, what would that be in tsps? Also .05 ml would equal what in tsps. I don't have a scale and reply on teaspoons to measure out my dry ferts.


----------



## dennis (Mar 1, 2004)

How would the plants taking up a lot of PO4 cause what Bryce is seeing? If he adds 4mg/l NO3 and 1.5 mg/l PO4 but at end of week he has 10mg/l NO3 and 1 mg/l PO4, then the plants are only taking up 0.5 PO4 for the week while adding 6 NO3 from organic synthesis (break down of stuff in water). Unless he is adding a lot of PO4 in some other form (which would be very hard for a hobbyist or true researcher to track) I don't see how that indicates any luxury uptake. Maybe I am not looking at it correctly though.....


----------



## Edward (May 25, 2004)

Guaiac_boy talks about 10:1 ratio, not concentration.


----------



## LindaC (Nov 7, 2005)

Hey guys, did you see my post, can you tell me if I'm on the right track - 1 ml KNO3 is equal to about 1/5th of a tsp? It's 0.21 ml; am I in the ballpark? If that's correct, then .05 ml of PO4 is?????


----------



## artemism3 (May 21, 2005)

Thanks Dennis! I figured something was wrong with my numbers. I guess the dog and my son fighting in the other room hastened my math!


----------



## dennis (Mar 1, 2004)

Linda, sorry to not answer your question well. I think you posted while I was posting as I did not see you last post....

My suggestion would be to mix a solution and dose by ml's or capfuls, etc. FYI, the caps on soda bottles hold about 7ml. I suggest you use the Fertilator or Chuck Gadd's calculator and mix a solution that provides the concentration you want in 1 (7ml) or 2 (14ml) doses. For example, according to Chuck Gadd's calculator, 2 teaspoons of KNO3 in 500ml H2O adds .14 mg/l NO3 per ml of solution. So, one capful is about 1mg/l at that concentration in you 29 gallon aquarium. It is much more accurate to mix larger amounts and dose from that, escpecially when trying to measure tiny amounts of dry chemicals by volume. The percent error you are likely to be off is less with a teaspoon that with 1/5th teaspoon.

But to answer your question, a teaspoon is about 5ml so 1ml is about 1/5th teaspoon. You'll never be able to measure .05ml with a spoon type measure but if you meant half of 1 ml, that is .5ml or 1/10th teaspoon. I know you can buy smidgon, pinch, etc spoons in Linens n Things, etc that measure in that, though I do not know what volume they are exactly.

Personally, if I were you, I'd buy a small gram scale. 0.1 gram measuring ability and limits over 100grams would be sufficient and can be had from eBay for about $20. I love mine!


----------



## LindaC (Nov 7, 2005)

Thank you Dennis, I think I will take your advice and make up a larger amount and dose that way.


----------



## dennis (Mar 1, 2004)

Your welcome. Also, for what it is worth, I mix most of my solutions in Coke or Dasani bottles. The ones that are like 12 or 16 oz (I forget which) but they hold about 600ml full. I know that on the Coke bottless, 500ml level is about 1/4" below the ridge where the neck of the bottle starts (in the flat area where the label is). With the Dasani bottles, 500ml level is to the bottom of the top most impressed pattern on the tapery part of the neck of the bottle.


----------



## LindaC (Nov 7, 2005)

Dennis, I plan on looking at Ebay this weekend for a scale, but I want to say this; I cut down on my KNO3 by one teaspoon and upped my phosphate a little and I see a noticeable difference in my tank these past 4 or 5 days and no algea at all. I also stopped dosing my micros and macros on the same day. Only hope I can keep it this way!


----------



## Glouglou (Feb 21, 2006)

Amazon river

Nitrate = 0,17
Phosphate = 0,02

Work with the 10:1 ratio....


----------



## BryceM (Nov 6, 2005)

One bit of advice about the scales..... I got one that has a capacity of 150g but it only measures in 0.1g increments. This is fine for dosing out larger quantities for a stock solution, but it's not as accurate for small quantities. The 0.01g scales are probably better for what we do, and as I recall, they aren't that much more expensive - maybe a few dollars.

Good luck with the tank. If the plants are doing well the algae issues should be minimal.


----------



## dennis (Mar 1, 2004)

Linda, your best bet to keep a healthy aquarium is to develop a routine and stick with it, changing things only slightly as need/observation dictates. I second what GB said about the scale. 

And now back off topic, IIRC, the 10:1 ratio- aka the Redfield ratio- was not based on water parameters but on dry plant weight analysis on some saltwater macrophyte. If I remember correctly.... I may not. It also seems likely that the Amazon River parameters now a days is not so consistent with "nature", what with all the deforestation, defoliation and agricultural "advancements" in the region. But, the Amazon is a big river so maybe those measurements are indicative of a region not extremely affected by human activity.


----------



## LindaC (Nov 7, 2005)

I just purchased a scale off of Ebay yesterday, this is the one I bought, please tell me it will work for as little as 1mg or even .05mg:

http://cgi.ebay.com/JENNINGS-JS-300...hZ010QQcategoryZ34088QQtcZphotoQQcmdZViewItem

What do you think?


----------



## MrSanders (Mar 5, 2006)

Looks good, it should work out just fine for ya... and the price is right! 



> please tell me it will work for as little as 1mg or even .05mg:


Just FYI, from the description it looks like the accuracy is to 1/10 of a gram, or one decimal place. mg as you had wrote would stand for milligram... much smaller measurments than we would ever need.... and I would imange a scale that accurate would cost a LOT of money 

At any rate down to 1/10 of a gram should prove to work out very well for you.


----------



## LindaC (Nov 7, 2005)

Thank you, I was hoping to hear that, these types of scales are very new to me so I appreciate your correcting my math.


----------

