EI Dosing-KH2PO4 dose vs. target range?
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Old 03-19-2013, 09:43 PM   #1
PlantNewbie101
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EI Dosing-KH2PO4 dose vs. target range?


Hi,
I'm trying to figure out a dosing regiment for my 55G (moderate planted, co2 injected, 2 54W T5HO, heavily stocked) aquarium.

1/2 tsp of KNO3 3X per week=31.59ppm (target 5-30ppm)
1/8 tsp of KH2PO4 3X per week=9.69 ppm (target 1-3ppm)
1/8 tsp of Plantex CSM+B 2X per week=.46 ppm (target .2-.5ppm)

I don't understand why the target of KH2PO4 is listed between 1-3ppm and with the recommended dose I'd be getting 9.69 ppm?

If I dosed the KH2PO4 at 1/32 tsp that would put it in the target range at 2.42ppm. Would also keep in within the 10:1 ratio.

Why is there such a big discrepancy with this particular Macro with the recommended dosage and target range?

Thanks for any insight!
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Old 03-19-2013, 11:44 PM   #2
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I am getting 0.59 ppm with 1/32 of a teaspoon, and 2.35 ppm increase in phosphate with 1/8 of a teaspoon.

Are you sure you did not enter something incorrectly?
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Old 03-20-2013, 03:41 AM   #3
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http://rota.la/

Plug and chug.

FYI, EI is meant to target those ranges, it's not meant to guarantee those ppm's in any and every case, you may need to tweak and should.

It's an approximation.

All methods are also.
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Old 03-20-2013, 11:17 AM   #4
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DarkBlade,
I'm using the calculator that Tom referenced...rota.la
I put in 40 USgallons (as that is the volume of my tank)
I put in the "result of my dose"
1/8 tsp
and come up with:
Your addition of 0.125 tsp/caps KH2PO4 to your 40.0 gal aquarium adds
Element ppm/degree
K 1.33
P 1.05
PO4 3.23

multiplying the 3.23 x 3=9.69

putting in 1/32 tsp
Your addition of 0.03125 tsp/caps KH2PO4 to your 40.0 gal aquarium adds
Element ppm/degree
K 0.33
P 0.26
PO4 0.81

I am using the result of your dose, as this has the tsp unit.

Thanks.

Last edited by PlantNewbie101; 03-21-2013 at 09:11 PM.. Reason: typo
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Old 03-20-2013, 12:40 PM   #5
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The calculator is assuming that KH2P04 conversion is 5.6 grams=1 tsp.

Last edited by PlantNewbie101; 03-21-2013 at 09:12 PM.. Reason: typo
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Old 03-20-2013, 01:09 PM   #6
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I might be entering something wrong. Anthony, I can't even get the numbers your getting. I forgot to put in the op that I was calculating for 40Gallons of water not 55 gallons. As said 55 gallon in reality is only 46.7 G--so I just deducted down to 40 for the displacement factor.

Last edited by PlantNewbie101; 03-21-2013 at 09:10 PM.. Reason: typo
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Old 03-20-2013, 05:24 PM   #7
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Aha, first, I used 55 gallons in the volume (since that's the only information you provided in your first post regarding aquarium volume).

In any case, that works out the difference in numbers.

Secondly, regarding some caveats of (any) calculator: when using volume measurements, they can be wildly inaccurate compared with mass measurements, since volume can be affected by the form of the chemical (i.e. powder versus prills, etc). This causes the density to change, and ultimately, the results will be always off unless you are using the exact same form, every time.

As for the 1/8 teaspoon measurement ending up being more than the amount when done via selecting the "Estimative Index" method in that calculator - I am not sure without checking the math more in detail.

When trying to calculate the exact obtained concentrations of the chemicals, I never liked to rely on calculators, since I could not be certain whether the math was correct or not (I always ended up just calculating it myself).
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Old 03-20-2013, 05:51 PM   #8
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The calculator tells you to dose 282 mg of KH2PO4 per dose and comes out as 1.3 ppm.

I actually personally dose 5 ppm 2-3x a week.

The errors may be in how the tsp are measured or a conversion thereof.

Still, that's not outside what I personal dose either.
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Old 03-20-2013, 06:00 PM   #9
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Quote:
Originally Posted by PlantNewbie101 View Post
DarkBlade,
I'm using the calculator that Tom referenced...rota.la
I put in 40 USgallons (as that is the volume of my tank)
I put in the "result of my dose"
1/8 tsp
and come up with:
Your addition of 0.125 tsp/caps KH2PO4 to your 40.0 gal aquarium adds
Element ppm/degree
K 1.33
P 1.05
PO4 3.23

multiplying the 3.23 x 3=9.69

So, putting in the 1/8th tsp is way over and the 1/32 tsp is much closer.
I don't know what I'm doing wrong?

Thanks.
The issue here is that yes, given the amount you listed, your addition of KH2PO4 will yield 3.23 You can't just multiply that by three unless you assumed that your plants had zero phosphate uptake for the week. Remember, these three doses get spread out over a period of time (usually a week) so they don't fluctuate as much. By the time you add your next dose, the ppm will have gone down some. Obviously considering a high bio load your tank may already have additional ppms of phosphates. Like Mr. Barr said, it is meant to me adjusted based on your situation.
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Old 03-20-2013, 06:40 PM   #10
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Darkblade,
Thanks. I was aware of the mass vs. volume when I began using the calc. I was just double checking my work that I had done on paper.

"As for the 1/8 teaspoon measurement ending up being more than the amount when done via selecting the "Estimative Index" method in that calculator - I am not sure without checking the math more in detail."

You get what I'm saying...if you have a second to check it out, I'd appreciate it. There conversion is 5.6 grams = tsp.

Tom,
"The calculator tells you to dose 282 mg of KH2PO4 per dose and comes out as 1.3 ppm." That I get...but I don't have a gram scale..if I did..problem solved. But just the 1/8 tsp calc comes in at 3.23 ppm. Again they are using the tsp=5.6 grams. I'm just hic-cupping on that one detail, even though it may be irrelevant when all is said and done, I'm just wondering why it's not falling within the stated range of 1-3ppm, now if that range was 1-10ppm, I wouldn't even bother looking twice.

Again, I am just double checking my numbers and being anal. I don't have a phosphate test kit and don't plan on getting one....that is why I'm choosing EI as a method, it makes the most sense to me and I don't have to be all anal about numbers and testing. I'm just looking closely before I start....then I can focus on other factors if things go astray...lighting & CO2.

HigherThinker, I do understand the concept of EI. I was only questioning a range value with no uptake factored in. From what I've read "Based on Tom Barr's Experiment" the daily intake is roughly NO3 1-4 ppm, PO4 0.2-0.6 ppm.

That 1/8 tsp yielding 3.23 ppm is 1 dose, delivered every other day which again is over the 1-3 ppm weekly target range. Unless that target range is per dose...

I think he called it Estimative Index for a reason and I thoroughly get what it means!

But what you say makes perfect sense as well if those numbers were not taking into consideration uptakes. I didn't even think of that. Thanks.

Last edited by PlantNewbie101; 03-20-2013 at 06:45 PM.. Reason: typo
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Old 03-21-2013, 07:23 AM   #11
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It's late, and I am not going to bother looking up everything now, but 1 teaspoon = 5.6 grams seems unusually low.

I found an MSDS that states the density is 2.3 grams / cubic centimetre, which is significantly different from the value used in the calculator (more than double!)
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Old 03-21-2013, 07:35 AM   #12
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Quote:
Originally Posted by Darkblade48 View Post
It's late, and I am not going to bother looking up everything now, but 1 teaspoon = 5.6 grams seems unusually low.

I found an MSDS that states the density is 2.3 grams / cubic centimetre, which is significantly different from the value used in the calculator (more than double!)
Hence why folks should see if the weight of a 1/4 tsp or whatever they chose is standard or not, but......even if not........they are still in good shape here with EI.

It's fine to be anal, as long as you actually get something out of it.

I do not think that is the case here, which is why folks often chose EI, it has a much large error range than other methods.
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Old 03-21-2013, 11:28 AM   #13
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DarkBlade48,
Interesting with the weight conversion factor being so off. So, that would make more sense as to why the 1/8 tsp measurement is way less than the ppm the calc gives.

Tom,
This all just comes up because my son wants to look at the charts and keep journal/observations on that end of things. So, that is why we are being anal and asking before hand, so in our case, we are getting something out of it in the *long run*. As for many, I agree, nothing is to be had from this conversation.

He should of put this in his original post and it would of cleared up the "why" he was inquiring in the first place. Live and learn. (Obvious, he will be testing and doing all that, me on the other hand would just like to "plug and chug"...lol...and just getting in the ball park is good enough for me.) He wants to go a bit deeper and realizes that he can only use the calcs as a rough guide and work things out for our tank through our own consistency & observation. So, I'll plug and chug and he can do the detail work and then we can compare notes.

We were planning on sending him to school with the salts and have him and his science teacher give me a measure of what my tsps/grams are with a decent scale. He just figured he'd ask, because we hadn't received them yet.

We have studied a bit of the different methods and feel that EI will work the best for me/us. We like the thinking behind it and it makes the most sense. We have read a lot that you have written and your questioning and back and forth with others. You make a lot of good points and I can understand your rationale. Your not arrogant, you give credit where credit is due and we have respect for your methods. You've inspired my son a lot. Last year, in 7th grade him and his team, actually won the Lexus Eco Challenge, first round and their study was on Invasive Aquatics plant species. I like that EI will work because of the non-limiting factor and he likes it because he will be able to tweak and find the critical points...again..win win. For me it takes the ferts out and leaves the lighting & CO2 to tweak more.

We were only questioning the calculation/calculator because the discrepancy seemed rather large, in our opinion. It just wasn't adding up and he wanted to be close in values for the charting over time and build up.

This is my sons account and he posed the original question. Being at school..well mom jumped in...

Thanks for the back and forth. I enjoy growing things and it's science for my kids. Either way it's a win-win for us all and EI will get us to where we are going, with lots of "wiggle room".

Now any more from PlantNewbie101 will be my sons post. Sorry kiddo for jumping in...change your password..lol..

Thanks.

Last edited by PlantNewbie101; 03-22-2013 at 12:15 PM.. Reason: typo
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Old 03-21-2013, 03:38 PM   #14
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Since it's a study for the son, you should buy a small cheap 0.001 gram scale off ebay for 20-30$.

End of story.

Then measure the weight/mass.
Then you can use the calculators as they were meant to be used.

The issue are: not all teaspoons are the same, not all moisture content in the salts are the same, nor the brand and grain sizes are standard.

If you test or measure and want to be anal, then you NEED to do it right.
If not, then do not bother.

Pretty simple.

This also is a win win since you/son can confirm the weights. They you do not rely on the web information.
I do not use dosing calculators, but I did this before they existed.
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Old 03-21-2013, 05:29 PM   #15
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Hi Tom,
I agree about getting the gram scale for him and will do that.

I think I will also get the other 55 gallon going so he can mess around as much as he wants, without any fish. That just might work well for growing things out and then putting them in the display tank and keeping the plants that will adapt going under less intense conditions. Hmmm...this got me thinking now and just might go down another path.

I'm not a weekend warrior scientist/chemist. I just want some green in the tank and like to keep things simple. If I could keep what he grows out under some lower light, non-co2 conditions...makes things easier for me....just hook him up with the high lights and co2.

Thank you for all the back and forth. I'm old school and prefer to think for myself. This was a good lesson on some of the newer tools we have to play with and their limitations in practice. Many people would prefer to blame the system for their failure, when all is said and done it comes down to our own lack of understanding that is causing the failure and not the system itself. Using these calculators as a guide line are fine but our own eyes, observations and understanding are what is going to make the difference. To many variables for anything to be cut in stone and 100% when it comes to aquaria in general.

Have a great day.
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