# Dry ferts - please help me with the maths



## daizeUK (15 Oct 2013)

I want to dose my 120L tank with *Potassium Phosphate* and *Potassium Sulphate*
I'm trying to figure out how many grams of each salt to add to a 500ml solution.  I want to work in grams rather than teaspoons so that I can work out how much salt to buy and how long it will last.

APF tells me to mix Potassium Sulphate like this:
_*Stock solution : *Add 6.5g of potassium sulphate to 500ml of water.  Dose 1ml per 10 litres Of Aquarium water 3 x week; this will add approximately 1.5ppm K _

SoI took this to the nutrient calculator at Yet Another Nutrient Calculator which tells me the EI target for potassium sulphate is 7.5ppm.  So I work out that to dose my 120L tank for EI levels I should add 60ml of the stock solution suggested above (120L/10L x 7.5ppm/1.5ppm).

The problem is that when I ask the calculator to work out how to make a solution based on that dosing and it didn't agree with APF.
These are the values I plugged in:
_My aquarium is  120L_
_using diy  fertilizers_
_I am dosing with K2SO4_
_using a solution_
_My solution container is 500 mL and each dose is 60 mL_
_and I am calculating for The Estimative Index _

I expected it to tell me to make the solution with 6.5g of potassium sulphate but it doesn't:
_To reach your target of 7.5 ppm K you will need to add *16.714 g* K2SO4 to your 500.0 mL dosing container.  Add 60.0 mL of that mix to your 120.0 L aquarium_

Why are APF and the calculator telling me different amounts?  Is one of them wrong or have I made a mistake somewhere?


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## John S (16 Oct 2013)

If I were you I'd read this:
http://www.ukaps.org/index.php?page=dosing-with-dry-salts

The calculations in this are based on 20 gallons, your tank is about 30 gallons so just add another 3rd of the powders. It doesn't need to be spot on.


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## ceg4048 (16 Oct 2013)

I completely agree with John. You are wasting your time and energy trying to calculate dosages to the nearest 1/1000th of a gram.

1 teaspoon of powders typically weighs about 6 grams, so just do the conversion and get on with it.

Also, if you are dosing Potassium Nitrate then you absolutely do not need to add Potassium Sulfate. So that's one less thing to calculate.

Cheers,


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## daizeUK (16 Oct 2013)

I've got no intention of measuring doses to the milligram and I totally understand that it doesn't have to be accurate but I get the feeling that the APF site is giving incorrect concentration advice there.  If I followed their instructions I would only be dosing 40% of the potassium I need (assuming the calculator is correct).

The phosphate calculations also seem to be inconsistent.  If I follow your guide and convert it into grams for my 30 gallon tank it works out as about 500mg KH2PO4.  The TNC calculator roughly agrees with this at 660mg KH2PO4.  The Petalphile calculator gives me 211mg KH2PO4.  I don't mind being inaccurate to say, 50% but this is just silly.  One of these calculators will either have me triple dosing at 300% or underdosing at 30%.

Tom advised me to use potassium sulphate since I already have 40ppm nitrate in the tap water (and enough magnesium, but no potassium or phosphate).  However you also told me this:


ceg4048 said:


> The dynamics of nutrient uptake and usage are generally optimized around regular and cyclic dosing.


Can you explain the biochemistry of why regular nitrate dosing would provide better benefit than adding 20ppm of nitrates via a weekly 50% water change?


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## ceg4048 (16 Oct 2013)

daizeUK said:


> One of these calculators will either have me triple dosing at 300% or underdosing at 30%.


But this is not a problem. There will still be plenty of nutrition, and that's why you shouldn't worry about it. Have a read of the thread EI Newbie, totally confused lol | UK Aquatic Plant Society

At the end of the day, we can always tailor the nutrient dosing to fit our objectives. You are not locked into any formula. You just have to avoid deficiency. The baseline dosing levels are so high that unless there is a flaw in flow/distribution you shouldn't see a problem no matter which recipe is used.



daizeUK said:


> Tom advised me to use potassium sulphate since I already have 40ppm nitrate in the tap water (and enough magnesium, but no potassium or phosphate).


 Yes, of course, that's true if it is confirmed that the NO3 levels are actually that high. But I never assume that is the case unless the plants themselves prove that I do not need to add Nitrogen. Nitrogen is at the very top of the food chain so I never make assumptions about it's availability. I always start first with the baseline and then withdraw the KNO3 to see if it makes a difference.




daizeUK said:


> Can you explain the biochemistry of why regular nitrate dosing would provide better benefit than adding 20ppm of nitrates via a weekly 50% water change?


Well, one of the reasons is that plants have two basic categories of  nutrient uptake. A low affinity system, which does not grab the nutrient molecules as eagerly, and a high affinity system, which aggressively attracts the nutrient molecules.

The low affinity system is enabled when the nutrient levels are high. This means that nutrient availability is high and the plant does not need to spend energy producing those high affinity proteins. They are expensive to produce. The resources can then be spent on other things.

When the nutrient availability is low, then the plant is forced to produce these aggressive proteins in order to ensure sufficient nutrient uptake.

So what happens is that when you dose high amounts infrequently, the nutrient availability skyrockets initially, growth increases quickly and the plant drops production of the high affinity system components. The plant calibrates it's systems to the high nutrient load. Then, later in the week, when the nutrient values decline, the calibration becomes invalidated. There plant now has more mass and expects to have the high nutrient load, but it is no longer present. Nutrient uptake rates decline and the plant then tries to engage the high affinity system.

All of these changes takes time. They don't happen overnight. So the plant is trapped in a continuous loop of switching from low affinity to high affinity while uptake rates suffer at some point in the loop. Over time this reduces their efficiency, and generally their health will suffer. Again, this does not mean that it will always happen, or that it always will be terrible. This is just a general pattern.

Cheers,


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## daizeUK (16 Oct 2013)

Thanks for that great explanation Clive!

I'm afraid my curiosity wouldn't let me leave the maths alone!   Perhaps it may not matter, but I didn't like not knowing which calculator to believe so I sat down and figured it out myself.

The EI target for phosphate is 3ppm, or 1ppm thrice weekly.
My tank is 120L therefore I need 1ppm x 120 = 120mg of Phospate thrice weekly, since 1ppm is equivalent to 1mg/L when dissolved in water.
The molecular weight ratio of phosphate to KH2PO4 is 94.97 to 136.09 = 0.7.
Thus to get 1ppm of phosphate I need to add 120mg / 0.7 = *172mg* of potassium phosphate.

If I've made any glaring errors then do point them out!  Otherwise my value is even lower than any of the online guides and calculators suggest.  I'd be interested to know why some of the suggested values were so much higher.


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## wet (20 Oct 2013)

Hi daizeUK.

As mentioned, it's not so important you get things exactly right, but I can certainly understand your frustration when tools do not work correctly.

I think you may be doing the calculation on my calc wrong.  Here are your numbers above, which match mine perfectly.  Are you sure you didn't pick K2HPO4 or something else?




 

Cool imgur upload thingy by the way, UKAPS!


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## daizeUK (20 Oct 2013)

Cheers wet,
That calculator uses 1.3ppm as the PO4 target for EI (if you ask it to calculate for Estimative Index), otherwise it does agree with my calculations exactly.  I used a target of 1ppm because Clive's thread says the EI target should be 3ppm per week.  I'm curious why other calculators seem to have completely different targets, e.g.  the TNC Calculator advises a dose of 660mg KH2PO4 which would give 3.84ppm or 11.5ppm per week which seems excessively high!  Clive's recommendation of 1/16 tsp per 20 gallons would give about 3ppm per dose.

So I'm wondering if there is a reason for these high doses, I suspect the latter is an arbitrary amount because 1/16 tsp was the smallest convenient measurement for that example, but I'm curious to know why the TNC calculator is recommending nearly 4x the EI target.


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## wet (20 Oct 2013)

I can't speak for the TNC calculator, but the PO4 targets for EI come from a Plantbrain post on his forum a few years ago. I just chopped it up a little and posted it back and everyone seemed pretty cool with it once we talked it out  Remember you can always pick one of the other presets, though, like EI Low Light or EI Daily (but only dose like every other day or something).

Here's the values for dosing in case you want to scroll through them. I find it interesting and kind of shows how close they all are. (Check out ADA and what AquaSoil adds vs EI for example.)

Links are breaking but here it is:
yet-another-nutrient-calculator/constants/dosingmethods.yml at master · flores/yet-another-nutrient-calculator · GitHub


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## wet (20 Oct 2013)

Whoops, I guess I never added the ADA stuff to the calc. If you guys want it I can get around to it.

Here it is with some explanation. Reverse engineered from Plantbrain's measurements vs recommended dosing on the bottle. It's totally weird though and I don't get how some of the bits work with ADA and combining bottles 

Links on the forum are trying to get too much data but it's below here:
using Plantbrains concentrations and rota.la to get ppm/mL, then manufacturer dosing. 

*NO3 is derived from total N as NO3 equivalent. There is some NH3/4 in ADA fertilizers. Use rota.la to get NH3/4 specifically


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## ceg4048 (20 Oct 2013)

As I mentioned in that thread I linked to, it would be better to forget about any differences in the various recopies. EI is not a recipe. It is a world view. It is a methodology and a perspective which owes no allegiance to any formula or any recipe. It is an exercise in irrelevancy because you can dose any value you want and it will have the same effect. You should not care or spend energy worrying about why Recipe X is higher than Recipe Z. There are plenty of things to worry about in a eutrophic, CO2 enriched tank. You should be worrying about how you will accomplish excellent CO2 distribution, NOT why Tesco cat litter cost so much less than the same brand found at Sainsbury's.

I do not limit myself to any recipe. When there are good reasons to use lower values, they can be used without any concern. If you want to use higher values then you can without any reservations whatsoever. You don't have to worry about toxicity or algae because nutrients don't cause algae. Dose whatever values necessary to ensure unlimited nutrient availability. THAT is EI. I do not care about the recipe. I've actually only used those numbers you see in the article a handful of times. I'm a an obsessive water column doser so I dump lots of powder into the tank just to see what happens.

Here is a tank obsessively dosed with 10ppm PO4 per week. Who cares?






Cheers,


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## wet (20 Oct 2013)

Isn't pushing your "world view" completely ignoring that some folks may look at their tanks differently than you do, and does your view consider that dismissing that or tools to help them may actually discourage them?

"I do not limit myself to any recipe."

Yes you do, dude.  Read your post again and how you dismiss others.


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## daizeUK (20 Oct 2013)

I am sold on the idea that unlimited nutrients offer the best growing conditions for plants and therefore EI provides the best method for a planted aquarium.

I'm not yet subscribed to the notion that chemicals can be added arbitrarily without regard to toxicity, unless you can point me to scientific evidence that shows that high nitrate or phosphate levels have NO effect on the health of ANY species I might care to keep in an aquarium - including sensitive shrimp species which are noted for their intolerance to nitrate, for example.  When I say no effect I also want to consider general comfort and long-term effects on longevity and organ function, not just that the animal doesn't drop dead tomorrow.

I'm also tight-fisted by nature and I prefer not to waste chemicals fecklessly if there is no further benefit to the plants 

If I understand correctly, Tom Barr proved that there is a cap to all nutrient and light levels beyond which a plant cannot grow any faster.  So, EI does have a recipe which is derived from these capped levels.  Assuming that CO2 distribution is perfect, what is the benefit to anything by exceeding these limits?

Thanks for your links, wet!  I hadn't realised the calculator was yours!


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## wet (20 Oct 2013)

I really like where you're going with this. 

Personally I am not down with dumping say 40ppm of NO3 (or moving CO2 quickly, or anything big and fast in an aquarium) into a tank with living things. I have the same mindset you do that even if I cannot observe behavioral issues, my thinking I *may* be raising toxicity in a tank doesn't jive. Like, it's not worth me even worrying bout it, especially when considering the max yield vs concentrations you cite from Tom. 

One more data point: Claus (the former Tropica guru, still guru) likes to under fertilize his tanks because he wants to limit growth. That can make for a nice easy tank 

I would suggest you start low, as you're intuitively doing, and then slowly ramp up. If you already have some established plants, watching them as you adjust dosing over weeks will tell you tons about the tank. Then post back about those plants and try more and harder plants. Or at least that's how I recommend it to new folks. It's fun that way


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## BigTom (20 Oct 2013)

daizeUK said:


> I am sold on the idea that unlimited nutrients offer the best growing conditions for plants and therefore EI provides the best method for a planted aquarium.
> 
> I'm not yet subscribed to the notion that chemicals can be added arbitrarily without regard to toxicity, unless you can point me to scientific evidence that shows that high nitrate or phosphate levels have NO effect on the health of ANY species I might care to keep in an aquarium - including sensitive shrimp species which are noted for their intolerance to nitrate, for example. When I say no effect I also want to consider general comfort and long-term effects on longevity and organ function, not just that the animal doesn't drop dead tomorrow.


 

You're asking for something that is impossible to deliver, unless you have a few tens of millions lying around in cash and want to commission the research yourself (if so give me a shout, I'm at a loose end).

If you're that concerned about fish health in relation to chemical addition, why are you running a high tech tank at all? EI is an arbitrary amount, simply designed to be nutrient unlimiting for any realistic tank setup. Why do you think that 'base' EI levels have no long term consequences for fish? Are you adding CO2? How are you determining a safe CO2 level?

Sorry to be a bit blunt, but building a straw man on fish health grounds is pretty weak, particularly in a high tech setup with all the associated possibilities for behavioural and physiological stressors. Do you have evidence that how you keep fish now has no impact on their comfort, longevity and organ function, compared to in the wild or in a completely optimal environment? How are you defining and measuring comfort?


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## daizeUK (20 Oct 2013)

I have seen a fair amount of scientific research on the effects of ammonia on fish physiology.  Sadly it is mostly aimed at commercial fish farms but some of it is relevant to aquarium fish and I have been particularly interested in research on the long-term health effects upon fish from sustained sub-lethal levels of ammonia.  The research can be hard to find, particulary research that is free to the public, but there is still plenty of information available in this area.

When I look into this sort of research I am defining and measuring comfort via physically measurable effects such as length of lifespan, gill hyperplasia, evidence of kidney damage etc.  These are all useful indicators on how much physical distress a fish is experiencing.  In the case of ammonia I am also looking at whether these effects are reversed once the fish is re-introduced to clean water or whether the damage is permanent.  Experimental studies exist that have measured all these things via biopsy and autopsy.

Thus I was hoping that something similar existed for studies upon phosphates and nitrates and that you guys might be able to point me to it.  Perhaps the most likely source would be studies upon the effects of freshwater river system pollution from agricultural fertiliser run-off.

My point is that the claim is being made here that it does not matter how many nutrients are added because it has no effect on the tank inhabitants.  I'm simply asking to see the evidence that this claim is based on.  If you think there is no evidence then how can the claim be valid?


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## Michael W (20 Oct 2013)

An interesting thread which may or may not give you guys some insight Dosing and fish health | UK Aquatic Plant Societyhttp://www.ukaps.org/forum/threads/dosing-and-fish-health.29715/page-2


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## wet (20 Oct 2013)

"Test it and see. I'm not going to answer this because you or someone else should do this, then they will know the TDS contribution from dosing." - Plantbrain

Exactly. Don't assume it. I feel like people are only reading half or less of Plantbrain's lessons.

I would not say there is anything matching daizeUK's request for definitive data in that thread. Yes there is Plantbrain's experience, which is valuable. But that is not definitive data.


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## Michael W (20 Oct 2013)

daizeUK said:


> My point is that the claim is being made here that it does not matter how many nutrients are added because it has no effect on the tank inhabitants. I'm simply asking to see the evidence that this claim is based on. If you think there is no evidence then how can the claim be valid?


 
To my understanding Its apparently really hard to get accurate data on specific parameters in the aquarium without being rich as Tom mentions. So for us as people who are doing this as a hobby its really hard if not impossible to give accurate data. Although looking at fert pollution in rivers may give some sort of comparison we must note that the main request is about the health of fish in a enclosed system so we can only use data from that to an extent. So really in order to answer you question it may be easier for you to experiment yourself like wet's quite from T.B. Even then you may have to look at ethical issues.Therefore asking for definitive data is quite a hard task. 

I'm sure members on this forum have experienced dosing large amounts of EI with fish in their tank without causing problems, maybe asking about their dosing levels and observations in their fish's health to see if there are any correlations rather than asking for highly technical evidence such as autopsies or similar.


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## daizeUK (20 Oct 2013)

Thanks Michael.  I'm happy to look for research myself if nobody has any links.  I'm afraid I'm not qualified to experiment myself, as I have no training in biology or veterinary science 

Just to be clear, I'm not questioning whether base EI dosing is safe.  Plenty of people use it and are happy with it and that's fine with me.  My concern is about the unqualified advocation of arbitrarily high dosing levels, especially without knowing if there are potentially sensitive species present.

For example when I see a blanket statement such as


ceg4048 said:


> Overdosing of npk or trace will not affect fish.


I'd like to know what this statement is based on and whether it has been tested on all species at all levels of dosing.  If not, then shouldn't it at least be qualified?  Where are the safe limits?  Which species are the exceptions, if any?


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## ghostsword (20 Oct 2013)

ceg4048 said:


> Well, one of the reasons is that plants have two basic categories of  nutrient uptake. A low affinity system, which does not grab the nutrient molecules as eagerly, and a high affinity system, which aggressively attracts the nutrient molecules.
> 
> 
> 
> ...



Been a member of the forum for a while now, and have read and discussed many things, but this is new to me..  and absolutely makes sense. I knew the plants take about two weeks to adapt to a change in dosing, but did not knew why.. now I know..


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## wet (20 Oct 2013)

I just wanted to restate it: so why over dose when you don't have to, especially if you don't want to maximize yield/growth, and the gardener intuitively feels safer limiting levels in their tanks?  *That's still EI if you want to argue about it*


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## wet (20 Oct 2013)

Also, another point: Plantbrain often suggests ramping down on dosing (start high, then back off).  I actually prefer this way as well on a new tank with no fish (because I do not add fish until my plants are growing and therefore uptake nutrients), but I think your plan of going up will work fine, daizeUK, especially going off some of your goals in the CO2 thread and easier plants to start.


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## ceg4048 (21 Oct 2013)

wet said:


> I just wanted to restate it: so why over dose when you don't have to, especially if you don't want to maximize yield/growth, and the gardener intuitively feels safer limiting levels in their tanks? *That's still EI if you want to argue about it*


That's your own personal paranoid intuition. Not that of EI, which does not address feeling "safer".

If you don't want to overdose then don't overdose. The point is that you don't have to be paranoid about dosing inorganic nutrients.You are making arbitrary and unqualified assessment of the effects on fish health and yet you have no data to show. We collectively have empirical data to show that there are no ill effects at the levels we dose. The toxic levels are orders of magnitude higher. The same cannot be said of CO2 or gluteraldehyde, or even fish food (since most people kill their fish by overfeeding). So it doesn't matter which recipe is used. Fish consistently breed in EI dosed tanks and they live as long or longer than fish in un-planted tanks.

So what we've shown is that if you want to lower the dosing you can, and if you want to increase, you can. You are not restricted in any way to any recipe or spreadsheet. This is an old argument. We've specifically dosed higher levels in order to show that there are no toxic effect of NO3 and PO4 at the levels we dose. There are plenty of studies out there on the toxic effects of NO3 for example:
 Studies on the toxicity of ammonia, nitrate and their mixtures to guppy fry 
There are other studies using guppy fry which show the NO3 toxicity (without ammonia) at over 700ppm. These are ridiculously high numbers that we never approach.

There are occasions where the so-called capped levels still result in deficiency. This is normally due to poor flow/distribution. The flow should be fixed, but oftentimes the hobbyist may lack the resources to accomplish that. A dosing increase can improve the situation in that case. The fact that we have been dosing standard levels, as well as higher values for years without any negative effects means that you can use any recipe you want and not quibble over a few ppm here and there. We've specifically pushed the limits in order to show that there are no ill effects.

In fact, it seems to me that you are contributing to the nutrient paranoia, and that your spreadsheet is presented as some kind of knight in shining armor protecting the world against overdosing. Meanwhile, in the real world, we can delete the spreadsheet and dose what we want without any care or worry. A TDS increase is the only penalty with eutrophic dosing.

EI dosing also means that you can lower the dosing values if you want to control the TDS or if you want to limit the water changes and maintenance. You can go in either direction without fear.

So that's why it doesn't matter which recipe you use and why few people care about spreadsheet numbers. There is no point becoming mesmerized with Spreadsheet cells and formulas. Just grab you teaspoon and get on with it. That's the whole point of EI, simplicity. No spreadsheets, no formulas, no ratios, no worries. The only other penalty of overdosing is wasted salts, but that's an economic issue.

I reiterate that there are plenty of things to worry about in a CO2 injected tank. Dosing is not one of them. Arguing about 1ppm versus 3ppm is patently absurd. Pick a recipe and follow it. Observe the plant's response, then make adjustments from there, based on real objectives, NOT based on paranoia.

Cheers,


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## daizeUK (21 Oct 2013)

Thanks very much for your answer Clive!



ceg4048 said:


> There are plenty of studies out there on the toxic effects of NO3 for example: Studies on the toxicity of ammonia, nitrate and their mixtures to guppy fry


This study is giving figures for the death rate after 72 hours at extremely high levels of exposure.  This is not particularly relevant to EI unless we're going completely mad with overdosing so I am more interested in studies which look at the long-term effects of moderate nitrate levels, e.g.  Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates .  This indicates that there are species of invertebrate and fish that should not be subjected to long-term exposure of the sort of nitrate levels that would be achieved with moderate EI overdosing.

Are you sure that EI can be used and overdosed as needed when there are sensitive species of shrimp in the tank?



ceg4048 said:


> So that's why it doesn't matter which recipe you use and why few people care about spreadsheet numbers. There is no point becoming mesmerized with Spreadsheet cells and formulas. Just grab you teaspoon and get on with it. That's the whole point of EI, simplicity. No spreadsheets, no formulas, no ratios, no worries.


 
Humour me for a moment, since these spreadsheets exist then I'd like to understand where they are getting their numbers from! 
I understand Wet's spreadsheet because it's clearly based on Tom's EI target values which in turn are based on his empirical values for maximised plant growth.  I can take these values as a guide and adjust them to my personal circumstances, for example increasing them if my flow is not perfect.  Why would a spreadsheet (or any other dosing guide) recommend higher values than these to begin with?  I'm just curious in case there is some ambiguity over the maximum phosphate levels than can be utilized by plants?

I suspect I may need to ask TNC directly to get the answer to this  but their spreadsheet seems to be out of action now.


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## ghostsword (21 Oct 2013)

I just dose EI according to the one mixture that Clive posted a few years ago. I do not measure amnomia, nitrates, ph, do not test for any of that. 

Only thing I do is dose lots (it is cheap), do two 50% WC a week, with 25% RO mixed in (as London water is very rocky) and that is it.. Simple.. 

Complicated is lights, flow and co2, that I need to spend time adjusting and getting just right for the scape in the tank.


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## daizeUK (21 Oct 2013)

Thanks Ghostsword but I am not debating whether EI is simple to use.

I don't need to know how the sun works in order to live.  The sun keeps me warm, it doesn't matter that it is a superheated ball of hydrogen and helium gas or that the surface temperature is 6000°C or that one day it will burn through its fuel and turn into a white dwarf.  The sun shines, it's that simple and I don't _need_ to know anything else.  I just like knowing


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## ghostsword (21 Oct 2013)

Maybe I misunderstood the post.. 

You want to know the maths to something that is as varied as anything in nature? 

I do not think that there is a mathematical formula that applies to all tanks and layouts. The fert companies would like us to think so, but no two tanks are the same, and a tank today is not the same tank next month. 

How can you measure the uptake of 10 plants in a tank, where the flow, co2 and light does not often grow exponentially with the plant growth, which in itself is dependent on the ferts you dose? 

So easier to dose above the level you may think you need, and hope that is enough, allowing to manage the areas you can such as light, Co2 and flow.


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## ghostsword (21 Oct 2013)

The spreadsheets are there as a comfort zone, as a guide, but in real life unless you know what you got on your tank, and experience on your side, you will more often than not make a judgement error, and either dose too much or dose too little. 

That is why aquascaping is more than putting rocks and wood in the right place, it is a balancing act and I believe that with every scape, every plant choice, every trimming, you are moving the goal posts and much adapt your technique to it.


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## daizeUK (22 Oct 2013)

I believe you're absolutely right but as you said, judging that balance is down to experience and I'm not at that stage yet!  As a beginner I have to choose a starting formula and this is purely a question of scientific curiosity to understand what I'm choosing.  I want to know where the spreadsheets get their numbers from.  I know Clive keeps saying it makes no difference and I am not going to argue with his infinite experience in that regard but whether it matters or not, enquiring minds still want to know! 

So my question remains, why are certain spreadsheets recommending higher doses than Tom Barr's maximum capped limits?

I can totally understand if a person advises me to dose at 3x EI.  I could ask you, Ghostsword, and you might make a rough judgement based on my plant mass and flow rate and lighting levels and you might personally recommend that I start dosing at 3x EI.  However spreadsheets are based on formulas and they don't usually pick arbitrary numbers out of the air, so there must be a reason for it to do that.

I realise I'm not likely to get a specific answer unless I ask the authors of the spreadsheet, hence the more general question - is there any ambiguity or controversy regarding Tom Barr's maximum EI levels that would explain the different targets between spreadsheets?


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## ghostsword (22 Oct 2013)

I think the best is to ask the authors..  

I started with Clive's formula for EI, which is based on a ppm of ferts in a tank when dosed daily, then I tweaked for the results I was getting, as my tap water also had an impact. 

Now I am in Cape Town, so surely I need to tweak again for the results I need, as the tap water composition is different from the one in London.

This was the article I used:
The Estimative Index (EI) Dosing with Dry Salts | UK Aquatic Plant Society
"
At this unlimited lighting we can then measure the uptake rates of the various nutrients. Since adding more light did not result in any higher uptake of these nutrients, the uptake rates measured under the unlimited lighting can also be considered to be unlimited nutrient uptake. On a weekly basis, these measurements were recorded to be the approximate values:
Nitrate (NO3) 20ppm per week
Potassium (K) 30ppm per week
Phosphate (PO4) 3ppm per week
Magnesium (Mg) 10ppm per week
Iron (Fe) 0.5ppm per week"


So there was a set of tests before those values were pulled out. 

I used that as a base for my own tanks.


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## roadmaster (22 Oct 2013)

Have you asked the author's?
I have seen formula's all over the place.Some take into account source water content,some are tailored for low tech,Non CO2, Some suggest no Pottasium due to that found in KNO3,KH2PO4.
Some suggest Equilibrium,GH booster for softer water. (Mg)
I think that's the appeal for some/many.You can start with non limiting amount and work down/up according to each application.
But I should ask the author's were it me.(I did)


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## ceg4048 (22 Oct 2013)

daizeUK said:


> This study is giving figures for the death rate after 72 hours at extremely high levels of exposure. This is not particularly relevant to EI unless we're going completely mad with overdosing so I am more interested in studies which look at the long-term effects of moderate nitrate levels, e.g. Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates . This indicates that there are species of invertebrate and fish that should not be subjected to long-term exposure of the sort of nitrate levels that would be achieved with moderate EI overdosing.


Yes, those data are for temperate waterways, not for tropical species. Also important to note is that they are not reporting the NO3 concentration level. They are reporting the "N" portion of the NO3. So because of the ratio of the weight of N to the entire molecule you have to multiply the N-NO3 value by 4.42 in order to get the NO3 concentration level.

So nitrate above 44ppm may be a problem if you are keeping rainbow trout or salmon, but that has nothing to do with tropicals.
Again, we've collectively been dumping these powders in tanks for years. No long term effects have been noted. Plants grow well and that helps the fish, because Oxygen is more important than anything else.



daizeUK said:


> Why would a spreadsheet (or any other dosing guide) recommend higher values than these to begin with? I'm just curious in case there is some ambiguity over the maximum phosphate levels than can be utilized by plants?


Well, I predict that you'll not get any good answers because nobody has tried to figure out maximum uptake of PO4. Folks just use the most popular recipes, ones that they know work and that they know they can suggest without any issues. As I mentioned, we've already demonstrated that there aren't any ill effects of high NO3, PO4, Fe content.

Cheers,


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## daizeUK (22 Oct 2013)

ceg4048 said:


> Well, I predict that you'll not get any good answers because nobody has tried to figure out maximum uptake of PO4.


Did Tom Barr not do this?  I thought he worked out the maximum uptake of all nutrients and that's where we get the 3ppm from?
Forgive me, I've been trying to find the link to his research all evening and I must be blind but my Google skills are failing me tonight


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## ceg4048 (23 Oct 2013)

It's unclear whether he directly measured uptake rates or whether he measured growth rates. Precise determination of uptake rate is extremely difficult. Growth rates are much easier to determine by measuring the dry weight. When growth rates don't improve with increased dosing then there is no point in dosing more. That's how he arrived at the baseline numbers. But he never cautioned against exceeding these values. He simply stated that using higher values was a waste of money due to negligible gain. His baseline numbers have nothing to do with toxic effects.

As Luis and others have pointed out, and what I've tried to explain, is that each tank is a little different and in Tom's test tank(s), his flow/distribution was good so he didn't notice any changes with additional nutrient loads. In larger tanks with poor flow however, it can occur that higher nutrient loads have an effect. Since there are no known toxic levels of PO4, a few ppm differences is not something worth worrying about.

In any case, whether you are concerned about toxicity or of being accurate, or both, we can tell you without reservation that:
1. Being accurate will not improve performance at all.
2. Other than higher TDS, there are no short term or long term negative impact of higher PO4.
3. In some cases, higher nutrient levels than baseline can show improvements in plant health.

We didn't just dream these conclusions up. It's based on what we observe in our tanks collectively, for around 10 years (including PMDD dosing strategy), as well as what we note in the scientific journals - as well as information directly provided by Tom Barr.

Higher nutrient loads typically result in higher levels of organic waste, and so this drives the need for higher maintenance, such as water changes. That's a good enough reason to use lower numbers. We're not necessarily advocating higher numbers just for higher numbers' sake. What we're saying is that there are no toxicity issues, and that sometimes, when troubleshooting poor performance, increasing the nutrient loading is a useful tool for isolating the fault. Since we never have to worry about toxicity we are free to increase or decrease as required to isolate the fault. So I, at least, specifically set out to dose much higher values in order to test this idea and to see where the limits are. It's easy to kill fish with CO2 or overfeeding, but it's very difficult to kill them or even to make them uncomfortable with KNO3, KH2PO4 or Trace mix. I and many others had fish breeding in EI dosed tanks. I've raised two successive generations of A. cacatuoides in an EI tank, so there are no long term effects of these salts at the dosing levels we are using.

Cheers,


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