# Adventures in Redfield land



## niko (Jan 28, 2004)

Not this kind of red field:









Joke aside - if someone doesn't know about this article and calculator please read it and save it. What you are looking at is what all methods and "methods" to run a planted tank are based on. And their variations too - the things we do with our tanks in the comfort and privacy of our own homes.
http://buddendo.home.xs4all.nl/aquarium/redfield_eng.htm

So in the last month I had a little of Blue Green Algae and a little of Green Algae in one tank. Both of these types of algae showed up as a result of playing with the N and P in my tank. Thing is - it all happened EXACTLY as described in the article above. If you think your algae problems are due to someting else then it maybe worth investing in a quality N and P test kits. And calibrate them before you use them.

*Here's my story:*
Setup an existing tank with new strong light + CO2. Put new plants. Substrate is inert.

Tested water - had N= 11.0 and P=2.5. Meaning NO3 and PO4 (note the distinction between N and P and NO3 and PO4 in the above article).

P=2.5 is too high. So I started to change water every other day to reduce the P to a normal level.
Plants grew very well, pearling heavily. Dosed daily Fe, K, and Traces only. No P or N dosing.

Got BGA. Tests showed P=1.85 and N=4.5. That means I had put the tank in the low-N zone and BGA were just a logical result.

Added KNO3 to raise the N to get away from the low N ratio. According to the easier to use "Buddy Ratio" I needed 10 parts N for each 1 part P. So for P=1.85 I needed N=18.5! But I was not going to raise my NO3 to 20. So I added KNO3 carefully over 3 days - to get the NO3 to about 12 and see if that will slow down the BGA. Also I knew that if I had to I could do 3 water changes (3 days) and lower that N=12 to about 2.0. That made me feel in control.

Well, I made a mistake. Notice how: I continued changing water. My P dropped to 0.4. And I was adding NO3.
At some point I see GREEN algae all over. They were not there 6 hours ago! How can I be in the high-NO3 area now?

Tests showed NO3=12 and PO4=0.4.

*So note the important points. * *Redfield in action!*
1. Low NO3 area: I get BGA in a tank with super pearling plants and changing water every other day.

2. High NO3 area: I get Green algae everywhere within hours.

At the moment the tank is at P=0.2 and NO3=8.8. Buddy ratio (supposed to be 7-13) is 44! Where do you think this tank is going? Hope you know now - green algae...
I will do another water change tomorrow to get the NO3 to 4. And I will have to add P up to 0.4. Buddy ratio of 10:1.

*Now notice 2 things here:*

*A.* Playing home chemist with your tank is a pretty dumb idea.
How long do you think I will be able to maintain an N ratio of 10:1? Not for long. So I will find my daily dosing schedule and keep it going. I do not call that smart. The tank is telling me what to do. If anything goes out of whack things go bad pretty much guaranteed. And if I have a lot of N and P as most of us like to have - that will happen VERY fast too.

*B.* Note how fast the Green algae showed up.
In a tank with excess nutrients floating in the water (say P=1 and N=10) there is plently of food to let the algae grow explosively. If my N ratios where messed up but I had say 0.05P and 1.0N how fast and how long do you think the Green algae could grow? Not much. They'd self limit. And don't forget - the plants are using the N and P too. So the algae will show up, but be doomed to stop growing pretty soon.

*Reasonable questions here are:*
- How do I keep the Redfield ratio within certain range without having to take care of my tank every single day or else?
- Will the plants be able to grow as fast if I keep the N ratio in the small numbers (say 0.1 and 1)?
- What happens if I let the plants eat all the food and stop growing - will algae take over?
- Does the Redfield ratio need to be so exact all the time?
- Does a tank always work as Redfield says?

I got answers or examples for some of the above questions. But let's see if there is interest in this thread.


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## rjordan393 (Nov 23, 2012)

I plan on using the Redfield ratio after I determine the uptake of nutrients. To determine this requires a plan of testing over a one to two week period. I already have my fertilizers set to give me the ppm I desire. The one to two week period and testing will tell me how often I need to dose. So I need to test each day until I need to intervene with another dose or even to correct the dose. 
What throws a wrench into this is that the aquarium will supply some NO3 & PO4 and I will have to take that into account. As long as the uptake of nutrients stays in a very close range, then I will know how much and how ofter to dose.
I tested my tank for NO3 & PO4 and they were 10 ppm & 0.7 ppm respectively on 01/16/13. I have purposely held off from dosing any more NO3 & PO4 since then. Now tonight, for the first time, my hygrophila corymbosa did not pearl up like they been doing. I think this tells me one or both of the ferts are at or near zero. I will know tomorrow morning when I test. 
The calculators that are available are only guides; so each of us will need to adjust the dosage amount and how often. I believe this is about the best, one can do. I too, want to be in a position so that I do not have to chase the numbers.
The key here is uptake. First learn what that is before adding ferts to bring them up to desired levels.


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## AaronT (Apr 26, 2004)

It does seem to work, though as you found out it's a difficult balance. 

I find the best method is to use a rich substrate and supplement the water column such it is available to those plants to look nicer with it, but nutrient accumulation is rather insignificant. 

Although, right now I'm dosing a fair amount of both N and P. I never have good results just dosing one or the other. Generally for me I target a 3:1 NO3O4 ratio as a launching point and I don't usually have to adjust too much from there. As you said though, this is different from the N ratio, which is what the whole redfield thing is about.

When I do adjust my dosing from this ratio it's usually in the direction of less PO4 giving me something more like 4:1 or even 5:1.


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## Yo-han (Oct 15, 2010)

niko said:


> *Reasonable questions here are:*
> - How do I keep the Redfield ratio within certain range without having to take care of my tank every single day or else?
> - Will the plants be able to grow as fast if I keep the N ratio in the small numbers (say 0.1 and 1)?
> - What happens if I let the plants eat all the food and stop growing - will algae take over?
> ...


This is quite a common method (Redfield) in the Netherlands, so I did started this way in the past as well. Here some of my experiences and of some others.

And a little side note as I know you're a big ADA fan, look at their tank parameters, they are usually within the margins of Redfield (PO4:NO3 0.1:1)

*How do I keep the Redfield ratio within certain range without having to take care of my tank every single day or else?*

Most people test twice a week to start with and adjust values. When you know a little about the uptake of your tank you can reduce it to once a week and later to once a month. As you said before, testing gets less and less important, looking at your tank even more. BGA add NO3, green algae add PO4. Or test to see whether you need to reduce the values first (important in non CO2 tanks).

*Will the plants be able to grow as fast if I keep the N ratio in the small numbers (say 0.1 and 1)?*

No, this works in a ADA system with a rich substrate, but with a inert substrate you'll notice that 0.1 and 1 will grow plants slower than 1 and 10. You get into PO4 limitation than. Basiccly you're doing the old Dupla or PMDD method, because other nutrients (mainly CO2) will be enough if plants grow slower.

*Does the Redfield ratio need to be so exact all the time?
*
No, not really. When you take a look at the table of the site mentioned in the first post. You'll see that a ratio between 1:8 and 1:20 is regarded as algae free. It is better to go to 1:20, because the first algae you get than is GSA, which most people find not as ugly as BGA.

*Does a tank always work as Redfield says?*

IMO yes, if not, there is usual a shortage of an other nutrient, traces, potassium or CO2. But when you go higher with the nutrients the ratio gets less important because you make a non limiting system. PO4:NO3 5:30 works just as fine IME. But working in a lfs I've seen hundreds of tanks with algae and every time I test NO3 and PO4 it is off.

I think it is a very cheap method for non CO2 tanks if you don't to spend your money on a rich substrate.


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## niko (Jan 28, 2004)

Yohan,

Thank you for the detailed response!

I wanted to ask you what exactly is Dupla's method and PMDD. Both of them have sunk into oblivion. I could not find 
info on Dupla other than their products on their website. But PMDD is explained here:
http://www.theplantedtank.co.uk/PMDD.htm

It is so weird that that website discusses the methods of running a planted tank but doesn't even mention ADA, El Natural. And substrate is mentioned only as a DIY project - not presented as having a major role. The site has a nice nutrient calculator though. I believe that that is actualy how most people see the hobby.

Can you add information on what is Dupla's method? And how does it differ from PMDD?
I believe this will be very useful information for new people.

Also - I am personaly interested in hearing what are the advantages of EI over PMDD according to you?


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## niko (Jan 28, 2004)

And an update on my tank:

I now have NO3=7 and P=0.17. That is still a huge shift of the Redfield Ratio toward growth of Green algae. 

What I see is that the BGA has changed color and does not appear that good (looks sort of wrinkled). Also the green algae that I did not scrub (on plant leaves) are reduced now - both number of strands and their length.

So in my tank I have a Buddy Ratio of 41 instead of 7-13, but the Green algae doesn't like the environment. I think that this has to do with the heavily pearling plants + the clean water after all the water changes. So it looks like Redfield is important but one needs to be reasonable of how close it needs to be maintained.

Another question here - do you know how ADA establishes the Redfield Ratio?


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## Yo-han (Oct 15, 2010)

niko said:


> Yohan,
> 
> Thank you for the detailed response!
> 
> ...


Dupla and PMDD are both based on low phosphate. Limiting growth and thus limiting CO2 requirement. Dupla is one of the reasons people still think PO4 causes algae. They started this rumor over 20 years ago.



niko said:


> Also - I am personaly interested in hearing what are the advantages of EI over PMDD according to you?


The advantages of EI, is fast growth (lots of plants to sell), but most important, I like to see what is happening. I never used PMDD but I think plants won't grow as fast as with EI or ADA. I started out with inert gravel and redfield, went on to EI and have a ADA style tank (the real ferts are too expensive, I make them myself).



niko said:


> And an update on my tank:
> 
> I now have NO3=7 and P=0.17. That is still a huge shift of the Redfield Ratio toward growth of Green algae.
> 
> ...


What kind of green algae do you have? I'll bet you'll devellop GSA if you keep the ratio this way. Other green algae like hair algae are not predicted by the Redfield ratio IMO. BGA and GSA are the markers.



niko said:


> Another question here - do you know how ADA establishes the Redfield Ratio?


I think ADA doesn't establishes it on purpose. Aqua soil has a great PO4 absorption, so PO4 in the water column will always be low. To saturate an cheap alternative aqua soil, like Marified Controsoil or Fluval Stratum with PO4 you need to add a lot of PO4, and 10ppm PO4 is 0 ppm in a few days. NO3 is a little higher because it is produced constantly by the filter, by converting fish waste (ammonia) into NO3. By doing water changes and making your plants grow good so they take up a lot of NO3 it won't be high, but 0 is almost impossible.


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## niko (Jan 28, 2004)

I am not sure if ADA doesn't care about the N ratio according to Redfield. But what is clear is that in their tanks the values of the different parameters are balanced with each other. While here in the US we talk about fertilizer concentrations, CO2-levels, and how to grow things fast (EI) ADA connects the different parts of the system in a very precise way. That's why I think the parameters in an ADA tank may seem off, but actually they are that way because they see the planted aquarium in a much broader way.

Here's an example:
As I understand there is a connection between the CO2 assimilation and the amount of available N. So if you have low CO2 the plants need more N to make it. But in an ADA tank the pH is 6.8 and the Nitrate is 1 or 2 ppm. It looks like the CO2 is too low AND the Nitrate is too low. But there are reasons why we see these values.

1. The liquid ADA fertilziers contain Urea (will not show as Nitrate and it is added in tiny amounts daily)
2. The available N is not only what shows on a test kit. There is an infinite supply of N in the substrate.
3. The pH =6.8 has to do both with maintaining reasonable plant growth rate AND keeping the biofilter from being exposed to low pH.
(http://www.aquaticplantcentral.com/...4-210-gallon-dutch-progress-2.html#post624832)
On the other hand the pH inside the AquaSoil substrate is lower than 6.8. From what I have seen with HC the roots love the acidic environment.
4. CO2 is 15-20. Both a good amount and not too much to lower the pH below 6.8.

So the way most of us look at an ADA tank is simplistic: "Aha! I see that ADA keeps the P at 0.1 and the N at 1. That's 1:10! That's what I need too."

So knowing about Redfield is important. But how it actually works in real life maybe very different. For example you said an interesting thing - that Redfield accounts for only Green Spot Algae (GSA). But I do not have any GSA. The algae that appeared because of NO3 overdose was green short hair algae. It appeared in the matter of hours but I have not seen it grow since yesterday when after a water change the Redfiled was still shifted toward green algae (Buddy of 41 instead of 10). Today I stirred the substrate a bit and did a big water change. N is now 5 and P is 0.28 (Buddy is now 18 ). I will leave them at that and see if this ratio is close enough for green algae to not grow.


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## BruceF (Aug 5, 2011)

This is good stuff. I’ve been adding fertilizers and keeping track of what and how much I add since last August. In the mean time I have had every kind of algae imaginable. Since I haven’t been using CO2 my only choice has been to keep altering the dosing. I can verify that this does work. I do have tanks with almost no algae. I can and sometimes do get GDA and GSA when I play with the N-P ratio. 
Keep it up!


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## niko (Jan 28, 2004)

I will tell you an interesting thing Bruce: Here I have a 55 gal. tank that I have let grow as much Cladophora alagae as it wants. The thing is the Clado is the short kind - like Marimo balls. It covers all the rocks and the gravel. It looks like a soft green mat. In the tank I also have 2 big piles of Java Moss.

This tank does not develop ANY algae. A reasonable guess would be that the Clado eats all the N, P and everything else. And this is the kicker - I tested the water in that tank the other day and the P was 2.5 and the N was 12! Yes, the P is way high and Redfield is shifted heavily toward blue algae. But the end result is a tank that doesn't grow blue or green algae. It doesn't even grow algae on the glass. Why the Clado is the only algae I do not know. The Amano shrimp are very hungry and go crazy when I add fish food to the tank - meaning that they have a hard time finding algae. In this tank I can add CO2 and make both the Java Moss and the Clado pearl. Or shut it off and let them be. No algae either way. If I reduce the P to normal levels and keep the N ratio shifted toward blue I guess I will have a tank with zero algae indeed. I guess there are algae because the otos that are in there are always fat. But I do not know why the shrimp act like hungry wolves and why no blue or green algae.


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## BruceF (Aug 5, 2011)

Niko I am interested in this idea that a stable ph leads to a healthy bacteria colony and therefore a tank with less algae problems. It suggests a few things like the possibility that problems with fluctuating co2 are in fact creating problems with the bacterial colony. 
Also I am curious about what people refer to as dirty tanks, like in the assertion that dirty tanks cause BBA and so forth. What does dirty mean in that context? Is it in fact a lack of O2? 
Finally I have a 10g tank with Dwarf Sag, there is no heater and there is no filter. In fact there is no water movement at all, once a week a change 50% of the water. Recently I added 6 Odessa barb fry (Nov 2). So where is the bacterial colony and why is it not ‘dirty’? 

Sorry if that is off topic.


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## niko (Jan 28, 2004)

When I say "dirty" I mean that there are enough organics floating in the water to cause BBA. In another thread we talked about something else though - if the plants grow well they do mke BBA disappear. Even if the tank has visible tuffs of waste on the plant leaves. 

So once again - it really looks like one needs to see the tank as a system of many parts. But the main thing that everything hinges on is the good plant growth. Tom Barr stresses on the plant growth but his EI skips everything else. It works, especially if you are the type that still enjoys to play with the ferts, but it sets a wrong mindset - that fertilizers are everything. Especially the fertilizers in the water.

More about these "organics". ADA always publishes a parameter that you may have seen - "COD". And in their tanks it is very low. It basically shows you how much Oxygen is being used in the tank. The amount of oxygen used is linked to the amount of organics. There are 2 ways to measure the Oxygen use (also called "Oxygen Demand") - biological and chemical. They are called BOD and COD respectivelly:

BOD (Biological Oxygen Demand):
If you have a lot of organics the bacteria jumps up to eat them. And the bacteria uses more oxygen. Simply put by measuring how hard the bacteria "breath" you know how much food they find on your tank.

COD (Chemical Oxygen Demand):
There also chemical processes that utilize the organics. Basically chemical reactions (no bacteria involved). They also use Oxygen. Simply put this is burning and burning uses Oxygen. 

ADA mesures only COD. I do not know if that's because BOD is harder to measure or what. But the bottom line is that their COD is low. Meaning that there are very little organics to be burnt (or eaten by bacteria).

You can find a COD test kit in the US only from ADA. And ADG or AFA will have to special order it for you. Meaning noone cares about their COD. As you see - we sit here talking fertilizers all day but overlook a simple thing like how clean is our water.


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## maboleth (Aug 13, 2013)

This is a very interesting stuff and I'm glad I found this! I came across the EasyLife's official site, where they mentioned the Redfield-ratio - the ratio I've heard for the first time and makes a lot of sense.

In a few days, I'll buy PO4 and NO3 test kits and see myself. I'm like 10000% certain that my tank suffers PO4 deficiency. The leaves of all plants, especially older ones, prematurely go yellow and die and I have loads of GSA without any BGA.


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## niko (Jan 28, 2004)

Focusing on anything specific is like hoping that the amount of salt will make or break the flavor of the entire meal. It is only one detail of the big picture.

You can have a perfectly clean tank with more P than N. You can have a tank full of algae with more N than P. Nail the Redfield ratio just right and you can still have ongoing issues.

My point is - do not focus on one thing. Look at the big picture. There is only one way to run a tank with the least issues and the least amount of work needed:

Rich substrate
Clean water (no fertilizers or very small amounts added and consumed daily)
pH as close to 7 as possible
Few fish
Strong light for a short time
As large biofilter as possible (10% of the tank volume is a good start)

All of the above can be tweaked but keeping the overall setup along those lines is the only best way to go. That is what El Natural is all about - and it can be made "high tech" if you manage to not lose track of common sense.

Every other approach is a game of chance, commercial and self serving goals, and forces a constant need for maintenance.


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## maboleth (Aug 13, 2013)

Thanks. I have already opened another post about identifying several issues that I have with the plants, so this redfield ratio is a good start to look for more.

My tank is generally healthy - water is crystal clear, all of my fish, shrimps and snails are lively and happy. Most of my plants seem fine, however I do have issues with several ones + lots of GSA on the glass.


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## niko (Jan 28, 2004)

You can reduce the GSA but do not fall for another popular notion - that GSA is normal. It is not. What is normal is to not care to understand how things work.

There are tanks that never develop GSA. I don't think anyone knows why. Find a recent thread by "happi" about "GDA" and how he found a way to eliminate them (GSA=GDA (spot/dot)).


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## Phil Edwards (Jan 22, 2004)

Here I was thinking that GDA meant God D*$% Algae. 

Interesting read Niko. I agree, a rich substrate + lean water column = stable tank. I'd argue that the Redfield ratio stuff isn't as relevant now as it was years ago before different technologies were developed. However, it's good to know to have a better "big picture" of what's going on in your tank so you can read the signs it's giving you.


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