Calculating Iron, Nutricalc and others differ

[Martin]

Hi.

I've been playing around with calculations.. Alot... alot alot..

anyway, I discovered a discrepancy which I cannot account for..

Perhaps you guys can?

If you look at the attachment (and I apologize for the quality, but there's not much room on this site)

You can see that all are same settings, but the result is different.

the spreadsheet are numbers based on Tropica's Aquacare product, then there's the fertilator from APC and finally Nutricalc.

All 3 should, in theory, use the same numbers, if taken from Tropica's figures, and the end result should be the same.. but it's not...

Can you spot the problem?

 

[Philosophos]

I'd say the issue here is paying attention to APC's Fertilator. I've played with both calculators, and the fertilator has a reputation for being flat out wrong often enough. I find nutri-calc rounds too much, and displays in confusing ways. My method has always been a .txt file and the calculator program that comes with windows. If I'm crunching a lot of numbers, I might make up an excel database.

IME it's better to design the calculator your self; if you're wrong, it's possible to know why. If a value or formula needs to be fixed, it can be. If you want to account for things like Ca:Mg ratios, it can be made to do so.

Trust your own work, check it over, get other people to look at your formulas. I don't use Tropica's products, so I can't comment outside of the information you've provided, but the math looks right to me.

-Philosophos

 

[Martin]

Hi Phil..
I would have to agree.. using one's own calculations is always better..
but this issue with nutricalc & the others..
now in my excel sheet, I cannot find any errors with the iron calculations.. and it is pretty much the same as fertilator..
but nutricalc differs greatly.. which is concerning..
I did my calculations prior to even knowing fertilator.. but I've been researching on calculators and this came up..
I am, as you suggested, building my own calculator on my website, based on my own calculations etc.

Maybe nutricalc is wrong? I emailed Dennis(quenton), creator of nutricalc, and he couldn't solve it at first glance..

to try and explain the calc. in the spreadsheet:

0,7(fe concentration)/(1000(litres)*1000) to get Mg/L
then result of MG/L*1000*Ml=ppm added..

so 0,7/(1000*1000)=0,0000007
0,0000007*1000*306=0,2142ppm


Make sense?

 

[Philosophos]

It makes perfect sense. If that's his method as well, I'd be willing to bet he's got issues with other parts of the code. I've never seen a fert calc that I trust. I don't even trust my own completely; I re-check the method and results frequently. One variable unaccounted for can change everything.

-Philosophos

 

[Tom Barr]

In general, I do not use the cals.

Great if it helps folks etc, but I have never relied on them, perhaps due to the fact they where after my time when I learned.
Once I learned, that was it.

I'm not so sure measuring Fe is going to get you far, estimation is also dicy.
Eyeballing the plants based on experience alone is the way/method I used and made the other factors, light(within user reason), CO2(within fish reason) and nutrients where all non limiting and then worked from there for Trace and Fe as a mere proxy for the other nutrients.

I used TMG to do this.

This seems to answer the question of what is enough for any situation.
I would use Tropica's reference personally.

Regards,
Tom Barr

 

[Martin]

Tom, I do agree, but since I am creating a calc. I cannot have a tick box saying 'eye the plants'

If people are adding 5x the amount of Iron/Micro when using nutricalc, something should be done..

 

[Philosophos]

It's hard to do anything purely because of the number of calcs that are out there. I think the best solution is the advice not to use them unless they're doing for you what you already know how to do. In that case, the calculator needs to be tested for accuracy before it's taken seriously.

-Philosophos

 

[Tom Barr]

I agree with both of you.

Not quite sure what to do.
Folks rely heavily (too much so IMO) on calculators and test kits in general.

They are good for estimating things.
However, that's all they do => predict.

It's not some absolution.

There is a range.
Still, 5x over is a bit ridiculous

No idea of help on finding the mistake, etc, but the eyes and plants are pretty good indicators.

Wasting 5x extra TMG cost a lot, wasting 2x KNO3 is not big deal.
So if you want to reduce the waste for ferts, traces are where to look at.

Regards,
Tom Barr