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Zorfox

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In response to many questions about dosing I've decided to explain my views on why we do what we do. I need a reference to send people to rather than repeating the same thing over and over. If anyone notices errors or problems please let me know since I will refer to this frequently.

It seems that most people learn "how" to dose fertilizers without understanding why those steps work. Learning the "how to method" first causes a lot of confusion when we finally ask the question, WHY?

We need to supply all the necessary nutrients to the plants in adequate quantities. Quantities that are high enough so the plant growth is never limited by the amount of any one nutrient. This idea is based on Liebig's law of the minimum .

Look at the barrel in this image. The water height of this barrel is limited to the lowest slat. Imagine each slat as a single nutrient and the barrel as the plant; the water height representing growth rate. Now the maximum growth rate will be defined by the lowest slat, or nutrient. So the growth rate of the plant would follow the nutrient in least supply.

So what would be the best option to get maximum growth rate from our plants? The answer seems obvious. Supply nutrients above the top of the "barrel". This would represent non-limiting nutrients.

Now we know the concept behind non-limiting nutrients. Let’s talk about the steps to obtain that condition. Again I'm going to use science. Hoagland's solution is nutrient rich water for plants to grow in. Sound familiar? Here’s what Wikipedia says about Hoagland’s Solution...
The Hoagland solution is a hydroponic nutrient solution that was developed by Hoagland and Arnon in 1933 and is one of the most popular solution compositions for growing plants (in the scientific world at least). The Hoagland solution provides every nutrient necessary for plant growth and is appropriate for the growth of a large variety of plant species. The solution described by Hoagland in 1933 has been modified several times (mainly to add iron chelates and the like), but the original concentrations for each element are shown below.
• N 210 ppm
• K 235 ppm
• Ca 200 ppm
• P 31 ppm
• S 64 ppm
• Mg 48 ppm
• B 0.5 ppm
• Fe 1 to 5 ppm
• Mn 0.5 ppm
• Zn 0.05 ppm
• Cu 0.02 ppm
• Mo 0.01 ppm
The Hoagland solution has a lot of N and K so it is very well suited for the development of large plants like Tomato and Bell Pepper. However, the solution is very good for the growth of plants with lower nutrient demands such as lettuce and aquatic plants with the further dilution of the preparation to 1/4 or 1/5. Hoagland solution must be made from 7stock.

Wikipedia, Hoagland's solution
Notice the nutrients listed as ppm (parts per million) above. The amounts in that list are far higher than we want in a planted tank. Remember, we have fish, shrimp, bacteria and an entire eco system in our tanks to worry about. In addition, the ratios are different for our purposes. So where do we turn now? We know we want to supply those 12 nutrients at various levels but what levels? Well, a hobbyist named Tom Barr thought the same thing. He’s determined the appropriate range for each nutrient through years of testing. The method of supplying non-limiting nutrients to our plants is known as the EI method or Estimative Index. I prefer the term EI concept because “method” implies a one size fits all mentality. This couldn't be further from the truth.

The ranges for EI are listed below.

CO2 range 25-35ppm
NO3 range 5-30ppm (KNO3)
K+ range 10-30ppm (K2SO4 or GH booster)
PO4 range 1.0-3.0 ppm (KH2PO4)
Fe 0.2-0.5ppm or higher (?) (Plantex CSM +B)
GH range 3 degrees ~ 50ppm or higher (GH Booster)

I know what you may be thinking. Where are all the other nutrients? And what does GH have to do with nutrients?

The "other" nutrients are supplied through one dry fertilizer called the trace mix. It's a combination of all the other nutrients mixed at the proper ratios, the most popular blend being Plantex CSM +B. The GH is listed as a nutrient because GH is a measurement of calcium plus magnesium; more on this below.

So from those 12 nutrients in Hoagland's solution we only have to deal with six. Nitrogen, Phosphorus, potassium, iron, GH and traces (the other nutrients).

We can dose nutrients using any frequency we like, daily, weekly or monthly as long as we stay within range. There are advantages to dosing smaller amounts over time. We get into a daily routine when we do something over and over. This helps us to remember to dose. It also prevents large swings which can impact some inhabitants. Most hobbyist with CO2 injected tanks dose every other day; macros one day micros the next. This can prevent nutrients in the trace mix from binding to macro nutrients, iron and phosphate in particular. However, low tech tanks can easily withstand monthly dosing with many other variations in between. Remember, EI is a concept not a step by step method.

Before we get into how to calculate doses let’s talk about water changes.

Clearly if we dose nutrients “above the barrel” there is a point at which some of them will become toxic. To prevent this we do regular water changes. The frequency of water changes is no different than the dosing schedule we choose. We can do water changes 3 times per week or once per year. It all depends on the system we happen to be running. The common theme being that we keep nutrients in a specific range. Balancing water changes and dosing schedules can easily be visualized using wets calculator.

As you can see, with a little tinkering on a calculator we can tailor any nutrient level we want. This is the easiest way to balance water changes and nutrients. Simply keep nutrients within the given range.

For new systems water changes of 2-3 times per week for the first 1-2 months can prevent many problems such as substrate leeching or absorption, removing nitrogen cycle wastes, and other problems we may face with a new setup. Many of these can lead to algae outbreaks and inhabitant stresses. All of which can be easily alleviated by frequent water changes and healthy plant growth.

To explain how we dose each nutrient let me use nitrogen as an example.

Nitrogen, represented by NO3 (nitrate) above. This is the result of nitrifying bacteria. This means we can have nitrogen without dosing. The amounts we have are based on the amount of organic matter that is processed by the bacteria. We can also get nitrate through our tap water. Many water supplies have nitrate levels from agricultural runoff. Since there are other sources for nitrogen we need to test for that first before we calculate a dose. In the list above the range for NO3 is 5-30ppm. If we will never go below 5ppm even after a 50% water change we may not need to dose nitrogen. If we will go below we should calculate how much is needed to keep nitrogen in that 5-30ppm range.

Let’s assume we have 0 nitrates and we want to calculate for 10ppm. Let’s further assume we want to dose every other day. If we want 10ppm then three doses per week would be…oh let’s just round it up say 4ppm. Notice we don’t have to be exact since the range is 5-30ppm! Always round up. We can taper off dosing later until we see changes in plant health. This nutrient level is called the critical point; the point at which nutrients become limiting. Just like everything else, this point is tank specific.

Now we have to figure out how much of something we need to add to raise NO3 to range. We can use a list of fertilizers to raise nitrogen. The most common one used is KNO3 or potassium nitrate. Below is a list of the common fertilizers used to raise the other nutrients within range.

NO3 (nitrogen) – KNO3 potassium nitrate.
K+ (potassium) – K2SO4 potassium sulfate. Found in many GH boosters as well.
PO4 (phosphorus) – KH2PO4 mono potassium phosphate
Iron (Fe) – Ferrous gluconate, EDTA iron chelate and DTPA iron chelate.
GH – Magnesium MgSO4.7H2O (Epsom salt) OR GH booster
Calcium CaSO4 (calcium sulfate) OR GH booster

Making these calculations couldn't be simpler. We simply use a nutrient calculator . There are many options on the calculator listed. Suffice it to say most people can figure out how to use the calculator rather than explain its use. This is how we decide how much of a fertilizer to add to raise that nutrient within range. The calculator can calculate for dry dosing or solutions, solutions being more appropriate for smaller tanks.

One point I would like to make in regards to the calculator output. Many fertilizers supply more than one nutrient as seen below. We need to keep a "running total" to account for this.

Notice how the KNO3 above also adds 2ppm of potassium?

We make these calculations for each nutrient in the list.

Three glaring issues still remain that we need to talk about; GH, iron and traces.

Gh, often noted as dGH (degrees of general hardness), is a measurement of the concentration of divalent metal ions such as calcium and magnesium per volume of water. Notice, other things can influence this measurement. However, calcium and magnesium are the two most valuable players here. Generally a GH of 3-5 degrees is considered adequate for plant growth. Sometimes the ratio of calcium to magnesium can be skewed to one side leaving the other out of range. So if we have access to a water report we can make an informed decision on whether we should dose additionally Ca or Mg based on total GH. This usually isn’t necessary. If we wanted to be safe we could add enough GH booster to raise the GH 1-2 degrees. This won’t have any impact on plant growth. It can however impact very sensitive fish and invertebrates.

Iron and trace mix are interrelated because most trace mixes contain iron. Many hobbyists have realized that higher iron levels are beneficial to multiple plants. Yet adding more of “everything else” is not needed. So a basic dose of trace mix is usually calculated to obtain an iron concentration of about .2ppm. That leaves iron at the minimum level while supplying sufficient levels of “everything else”. If we want to add additional iron we can use various forms of it.

Iron comes in many forms. The two basic types are non chelated or chelated. Essentially, chelated is a fancy name for time released. We can use iron without chelates which will last a short time, hours. This would be analogous to an injection from your doctor. It won’t last long but it works fast. We can also use iron that has been chelated with various chemicals. The time it lasts and the availability to your plants depends on the chemical used. The two most popular are EDTA and DTPA. EDTA can last up to 24 hours depending on the PH of your water. EDTA is the form of iron used in Plantex. DTPA can last up to 48 hours and is even more dependent on your PH. The higher the PH the more need for a stronger chelate such as DTPA.

So now we know why we need to dose, what we need to dose, how much we need to dose and more importantly, how to do it. Many debates are forged arguing levels, which fertilizer works better, or many other factors. The root issue always remains the same. Supplying non-limiting nutrients is the most efficient method to obtain maximal growth rate.

Rak9378

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Great post! Thanks Zorfox!

Zapins

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Very nicely explained.

plantbrain

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Just add enough ferts to not run out of anything even at high light/growth tanks and then do a water change to prevent anything from building up.

Hobbyist have done this same thing for many decades with fish, they "dose" fish food, LOTS of it to grow the fish well, then do frequent water changes to prevent waste/build up.

Hardly my idea. I just argue for it since it's simple and easy. I think many get all into the details too much really. Which is fine and all, but the question is you do not want to spend too much worry over ferts as a newbie, rather, light and CO2. EI just makes ferts independent for any planted aquarium, so you can focus on light/CO2. That is the main goal.

One of the biggest problems folks had were based on old myths about the dangers of excess ferts when I suggested this in the 1990's.
I thought those ideas were correct myself, but then noticed they could not be.

Zapins

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One of the biggest problems folks had were based on old myths about the dangers of excess ferts when I suggested this in the 1990's.
I thought those ideas were correct myself, but then noticed they could not be.
This is partially true.

Macro ferts have much higher toxicity levels than micro ferts do. Heavy metals are many times more toxic and have fairly low toxicity ranges, some like copper well below 1 ppm (0.15 ppm actually). Long term exposure to heavy metals makes the toxic concentration lower.

Zorfox

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Thanks guys. I think it's more important to understand a technique rather than following the steps of one. Without understanding, when problems arise, we have no idea where to turn.

Hobbyist have done this same thing for many decades with fish, they "dose" fish food, LOTS of it to grow the fish well, then do frequent water changes to prevent waste/build up.

Hardly my idea. I just argue for it since it's simple and easy.
Give yourself a little credit. It matters little that others have noticed improved plant growth with a given technique. Describing a common application and improving it happens to be the birth of many new discoveries.

“Discovery consists of seeing what everybody has seen and thinking what nobody has thought.” Albert Szent-Gyorgyi

Jack Gilvey

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This is a great post and I appreciate the effort it must have taken.

Thanks guys. I think it's more important to understand a technique rather than following the steps of one.
Sure it is, as in "teaching a man to fish" - I get it. Still, as evidenced by the daily posts here, the vast majority want to be told exactly what to put in and when - they just want to be given a fish for today.

anfield

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According to the nutrient calculator, using the EI low light weekly dosing, I would have to add 22ml of Flourish Nitrogen once a week to my 40g tank? Surely that can't be right?

NanoDave

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Thank you for the in-depth take on why we do what we do, or should be doing for that matter.

STS_1OO

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Excellent post Zorfox. Folks like you bring some real value to these forums and the effort is much appreciated.

KribsDirect

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This should be put with the FAQs.
Thanks for taking the time to write this up. I've been looking for more info I could understand about EI. I just bought some ferts from Nilocg for a tank I'm building while still unsure of what I'm supposed to do other than just follow the dosage instructions. This was very helpful in learning more about it.

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plantbrain

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This is partially true.

Macro ferts have much higher toxicity levels than micro ferts do. Heavy metals are many times more toxic and have fairly low toxicity ranges, some like copper well below 1 ppm (0.15 ppm actually). Long term exposure to heavy metals makes the toxic concentration lower.
That is rather tough to do, I've tried.

I'm sure you could dose enough, but it would REQIURE gross error, massively so, on part of the aquarist, I've never once seen this in some 15+ years of experience of helping folks on line.

Can it occur? Sure, will it? Well, 15 years is a long time and lot of folks have made some really large errors thus far, no one's done it yet near as I or anyone else looking for me can tell.

I've dosed 100-200X what I am suppose to, dosing pump dose it all at once because I did not set the switch on the pump correctly. No death, but a nice yellow red color in the tank. that was with SeaChem Flourish and TMG. Maybe CMS will?

No one has show that to be the case yet, so for macros and micros, you need to get 10X or more dosing errors before you see risk which is a wide wide error range.

Partially true?
I've had these same discussions for nearly 20 years perhaps 100 times now.
Shrimp, fish die for many reasons, even without plants and such.......we have to exclude those possibilities prior. If we have a case where they have not died and done well in spite of the high dosing of Traces........well, that falsifies the claims.

That's how it's done, not correlation alone.

Now if we cannot dose say 10X the suggested amount, then we cannot say it's the trace, but perhaps likely it is, but we cannot rule other basic aquarium causes either.

If the livestock is fine, and plants etc are doing well over time, then we can rule out Traces and rule out basic aquarium care/other causes for death since the livestock is doing well. This is basic logic.

When you say a specific hypothesis, liek traces kills things, cause algae, whatever..........you are best off stating a specific ppm etc, say

"0.2 ppm Cu from CMS+B will kill 50% CRS if you dose this amount daily for 4 weeks."

Now you have something to test and to try and falsify. Generalizations are near worthless. They offer little to the knowledge base for aquarist.

plantbrain

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Thanks guys. I think it's more important to understand a technique rather than following the steps of one. Without understanding, when problems arise, we have no idea where to turn.

Give yourself a little credit. It matters little that others have noticed improved plant growth with a given technique. Describing a common application and improving it happens to be the birth of many new discoveries.

“Discovery consists of seeing what everybody has seen and thinking what nobody has thought.” Albert Szent-Gyorgyi
Arguing for logic, I'll accept that, but not the idea.
Discus folks had been doing it and I figured there's no reason to test if you make a reference solution 2x a week basically with 50-80% of the tank water.

It was mostly to get away from test kits.
It also worked well because large water changes mitigate CO2 and algae issues.

I've yet to meet a single person who got into the hobby that was interested in testing NO3 and PO4, and such. Gardening? Yes, Water changes are part of the labor? Certainly.

Can water changes be greatly reduced using EI? Yes. In fact, that's one of the goals once the user get some good observational experience. I do many on my 120 Gallon Dutch tank, but I move stuff around a lot, have a messy sediment that makes muddy messes, uproot etc, so it's more to keep it clean than anything to do with fert management. The other Buce tank gets a water change once a month. Light is less, dosing is less, uprooting virtually non existent. Taken to the end point, you do with non CO2 enrichment/no excel and low light with rich sediments and perhaps dosing 2-4x a month, maybe 1/10th EI doses.

No set method will be all things to all goals, but a conceptual approach will allow someone to adjust and understand how to do it.

In terms of light and CO2:

http://www.tropica.com/en/tropica-abc/basic-knowledge/co2-and-light.aspx

This covers virtually 100% of all planted tanks in terms of light and CO2.
They used non limiting ferts for the test.

If you add ferts to the table 1 matrix, now you'd have 9 x 3 boxes....(for 3 levels of ferts).

Best to manage light 1st, then if that's too much, manage CO2 next, then lastly........ferts, as CO2 and light are the main players.

Ferts are easy frankly. Aquarist make them complicated.:icon_cool

Zorfox

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According to the nutrient calculator, using the EI low light weekly dosing, I would have to add 22ml of Flourish Nitrogen once a week to my 40g tank? Surely that can't be right?
Can't it be? Let's look and see why that makes sense. This is a good time to explain why water changes and dosing amount and/or frequency are closely related. Changing either will significantly impact the other.

We have 40 gallons of water we want to dose.

Using a nutrient calculator, it recommends 22ml of Seachem Nitrogen for low/light weekly EI dosing. The 22 ml dose raises NO3 (nitrates) to 10 ppm.

The range we want to maintain is 5-30ppm of NO3. So 10 ppm is in that range. Great!

Below are a couple of graphs from wet's calculator. We enter the PPM, the dosing frequency, water change amount, and finally water change frequency.

The first image is 10ppm weekly and a 50% weekly water change.

Notice how that 5-30 ppm range for NO3 are seen for each uptake group? This uptake percentage (ratio) will be driven by many factors but the most important two are light and CO2 (excel included). So the uptake ratio will change based heavily on which type of tank we have, "low" - "high tech".

The image below depicts the same 10ppm weekly dose of NO3. However, we changed the water changes to 50% monthly.

Now we see a huge change. Our range is from 7 ppm - 75 ppm! That range has crumbled away without weekly water changes. Not to worry. If we don't want to do weekly water changes we can adjust our dose. Changing the weekly dose to 3.5 ppm we can stay within the range we want using monthly water changes.

This concept is important to understand. Modeling nutrient ranges in this way can predict very accurately what we can expect to see based on our own maintenance schedules. A "one trick pony" way of dosing for EI or any other method is not necessary. EI is NOT simply daily dosing and weekly water changes. It can be scaled to any application you wish.

Zorfox

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It was mostly to get away from test kits.
It also worked well because large water changes mitigate CO2 and algae issues.

Can water changes be greatly reduced using EI? Yes. In fact, that's one of the goals once the user get some good observational experience. I do many

No set method will be all things to all goals, but a conceptual approach will allow someone to adjust and understand how to do it.
It's funny I was writing my response above when you posted this lol.

I agree it needs to be mentioned the thought process behind why you initially conceived this. Balancing water changes with dosing eliminates regular testing not to mention the other benefits to regular water changes. From my experience however, most new and many old hobbyist never learn the basics of nutrient management. So they usually get stuck into following a dosing regime without understanding how to adjust. This basically prevents them from ever making those needed changes based on their own tank. As you said nutrients are easy. This is especially true when you understand the basics. Without that knowledge, it's like the difference between riding a bus and driving your own car. The bus will take you where it wants to go. Drive a car and you decide where to turn.

anfield

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Zorfox, thanks, it makes sense, to be honest I was just shocked at how quickly I would burn through ferts. Not too different from dosing drugs and pharmacokinetics in humans.

According to the tropica article that Tom Barr linked, seems to indicate that nitrogen and phosphate supplementation are not required for well stocked planted tanks?

Some great info in this thread, will definitely be bookmarking it.

Zorfox

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Not too different from dosing drugs and pharmacokinetics in humans.
Maybe that's why this makes sense to me. Nearly 30 years of dosing patients. Administration types, therapeutic levels, clearance times etc. all relate to this. All the way down to the acid base balance system used to interpret blood gases.

According to the tropica article that Tom Barr linked, seems to indicate that nitrogen and phosphate supplementation are not required for well stocked planted tanks?
Yup. Remember this from the initial post.

"Nitrogen, represented by NO3 (nitrate) above. This is the result of nitrifying bacteria. This means we can have nitrogen without dosing. The amounts we have are based on the amount of organic matter that is processed by the bacteria. We can also get nitrate through our tap water. Many water supplies have nitrate levels from agricultural runoff."

Phosphates are another thing we can see from a well stocked tank. Accounting for endogenous nutrients is easily done when we understand the basics.

ipkiss

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Zorfox, thanks, it makes sense, to be honest I was just shocked at how quickly I would burn through ferts.
Anfield,

This is why we buy dry fertilizers and mix them ourselves. Your 22ml of flourish will finish that bottle way too fast. Get a pound of KNO3 dry fertilizer from someone like nilocg on the sales forum and it'll be way more economical.

Zapins

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I'm sure you could dose enough, but it would REQIURE gross error, massively so, on part of the aquarist, I've never once seen this in some 15+ years of experience of helping folks on line.
Not as high as you'd think depending on the micro we are talking about.

I've dosed 100-200X what I am suppose to, dosing pump dose it all at once because I did not set the switch on the pump correctly. No death, but a nice yellow red color in the tank. that was with SeaChem Flourish and TMG. Maybe CMS will?

No one has show that to be the case yet, so for macros and micros, you need to get 10X or more dosing errors before you see risk which is a wide wide error range.
Two things,
Flourish is quite dilute, so 200x a normal dose isn't that high of a concentration. CSM+B is much more concentrated being in dry form so I'd expect that to be more likely to cause an overdose. Compared with a 200x overdose on CSM+B which would almost certainly ruin a tank.

When you dose a concentration a given nutrient the short term effects of a toxicity are not seen unless the concentration is very high. That is why ~1 ppm copper is considered "toxic" to algae and plants for a short term exposure (1-3 days). If you increase the exposure time to a few weeks copper becomes toxic at 0.15 ppm, possibly even lower, to many plants. The recommended dose for copper is below 0.02 ppm to avoid any sort of inhibitory effect.

Partially true?
I've had these same discussions for nearly 20 years perhaps 100 times now.
I can ask the same question of you. Please support your statements with actual scientific background literature. It is very easy to refute another person's argument, but much harder to support your own with published long term study evidence, or peer-reviewed literature based arguments.

My work-in-progress literature research into toxicity ranges (mainly for unchelated micros):
http://www.aquaticplantcentral.com/...eficiency-literature-research.html#post661246

I am fairly certain you have already read the CSM+B iron toxicity thread where I provided background research and thought on the matter but here it is again so you don't have to search for it:

Shrimp, fish die for many reasons, even without plants and such.......we have to exclude those possibilities prior. If we have a case where they have not died and done well in spite of the high dosing of Traces........well, that falsifies the claims.
The effects of certain concentrations of nutrients on shrimp and fish have been extensively studied and there are very well documented LD50 values for that. Copper is one of those that has been looked at very thoroughly. So when you say we have to exclude those possibilities when trying to figure out if high traces makes a difference I disagree. It is very relevant. If we are reaching known values for toxicity or even approaching a fraction of those values then we are entering dangerous territory.

Furthermore, there is no need to overdose micros (except possibly iron), plants simply don't use that much of them. Have you ever seen a molybdenum deficiency? A copper deficiency, manganese? Do you know that many researchers actually have difficulty keeping their sample water pure enough to actually demonstrate a deficiency of many of these micro nutrients? What benefit do we get from massively overdosing traces when we know - from hundreds of studies - that heavy metals can and are toxic to fish, shrimp, plants, bacteria etc at very low concentrations...?

Now if we cannot dose say 10X the suggested amount, then we cannot say it's the trace, but perhaps likely it is, but we cannot rule other basic aquarium causes either.
Many studies I have read also talk about ED05 or ED10. Basically the dose that it takes to negatively affect 5% or 10% of the plants. Do you think we can easily see toxic effects on plants if they are at the lower end? Affecting only 5-10% of the plants? Does that make the toxic effects on our tank inhabitants any less concerning if we are aiming for unlimited healthy growth?

Again, I see no point overdosing micros when 99% of the time you'll never get a micro deficiency even with very low concentrations. On the other hand toxicity is a very real possibility and there are documented literature values where researchers have exhaustively tested and found low concentration effects.

What about people who have naturally higher levels of certain micro nutrients in their tap water? What happens when we add very high trace nutrients to their tank? Both doses combine and you can fully enter toxic ranges.

What about people who have small tanks and accidentally add a teaspoon of micros 3x a week? A teaspoon doesn't seem like that much to a beginner, but in a small tank it can quickly reach toxicity levels especially since plants don't use up micros as quickly as they do macros.

When you say a specific hypothesis, liek traces kills things, cause algae, whatever..........you are best off stating a specific ppm etc, say

"0.2 ppm Cu from CMS+B will kill 50% CRS if you dose this amount daily for 4 weeks."
I never said they cause algae. I said they damage plants when micros reach certain ranges.

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