Thread: Fertilator Conversion Factors

1. Lifetime Charter Member
Join Date
Mar 2009
Posts
1,346

Fertilator Conversion Factors

So I'm building my own databases right now to take care of fertilizer calculations. Since so many people use APC's Fertilator for their calculations, I decided to get the grams/teaspoon conversion for anything listed in dry weight. These numbers are rounded now and then, but not by very significant amounts:

Nitrate NO3:
KNO3: 5.2g/tsp
Ca(NO3)2.4(H2O): 4.8g/tsp

Phosphate PO4:
KH2PO4: 5.6g/tsp
K2HPO4: 4.5g/tsp
NaH2PO4: 4.5g/tsp
Na2HPO4: 4.5g/tsp

Potassium K:
K2SO4: 6.4g/tsp
KH2PO4: 5.6g/tsp
K2HPO4: 4.5g/tsp
K2CO3: 4.5g/tsp
KCl: 4.5g/tsp
Seachem Equilibrium: 5.33g/tsp

Calcium Ca:
CaCO3: 1.2g/tsp
CaCl2: 4.4g/tsp
CaCl2.2H2O: 3.6g/tsp
CaCl2.6H2O: 4.5g/tsp
CaMg(CO3)2: 5.2g/tsp
Ca(NO3)2.4(H2O): 4.8g/tsp
CaSO4.2H2O: 3.1g/tsp
Seachem Equilibrium: 5.33g/tsp

Magnesium Mg:
MgSo4.7H2O: 5.1g/tsp
MgCO3: 4.5g/tsp
Miller Microplex: 3.9g/tsp
CaMg(CO3)2: 5.2g/tsp
Seachem Equilibrium: 5.33g/tsp

Iron Fe:
CSM+B: 4.3g/tsp
Miller Microplex: 3.9g/tsp
Seachem Equilibrium: 5.33g/tsp
10% DPTA: 4.4g/tsp

If anyone has weighed these compounds and figured out their volume in a more accurate method, I wouldn't mind listing those numbers either. Fertilator density measurements are based on a bunch of different people's measuring cups and teaspoons that have obviously varying accuracy when one looks at the Fertilator threads.

-Philosophos

2. Thank You!

Thank you Philosophos. Nice work!

I kind of always figured there was a bit of slop in the calculators, just really do not have the brains or inclination to do what you did.

For all the folks who link to APC when someone recommends dosing half a gram more than the ‘Fertilator’ or some other ‘calculator’, have a good read.

The great thing about EI is that with weekly water changes it gives a place to start. It is nice to have the quantitative analysis, lets us have a feel for the size of the 'ball park.'

Biollante

(This in no way should be construed as saying CO2 and good circulation are not important, without a doubt CO2 is more important by far than anything except lighting, which indeed drives the process.)

3. This helped and is helping me a lot. Thanks.

4. Couldn't you use their specific gravities and calculate the tsp weights?

5. Lifetime Charter Member
Join Date
Mar 2009
Posts
1,346
Specific gravity would presume that it's a solid block of one of these nutrients. These are powders; plenty of air, static, moisture, etc. to deal with. These numbers are also the fertilator average; if you dig back through some threads you'll find that the maker (can't recall his screen name) just took mass consensus from APC as to their weight of a compound per cup and averaged. Some measured with their lab equipment, many with their kitchen measuring cups. Some had scales accurate to .001 of a gram, others had balancing scales accurate to 1 gram. Some people kept their bags at zero humidity and took out what they'd use in a short period of time, others had them in things like 80% relative humidity and opened them daily.

There's lots of room for error with fertilator, but so many use it that it's nice to have their conversion factors for dry dosing. It's also handy to check their numbers over. I put the values for some of the more common compounds above into a little spreadsheet just for checking over people's math who use fertilator but don't know how to make the calculations themselves. It's saved me countless hours of playing with a calculator.

Personally though, I just try to convert people over to at least using a scale to measure out daily values for dry dose. Stock solutions are pretty handy too.

6. I like stock solutions, thanks to you guys. The only ferts I dose dry are Equilibrium and K2SO4.

7. Lifetime Charter Member
Join Date
Feb 2008
Posts
53

Effect of RH

The wt per tsp tables will be certainly be useful for administration of dry measures.

As mentioned previously, it is important to be mindful that many of the mentioned salts are hygroscopic, like calcium chloride Thus, the wt may vary by relative humidity and temperature.
This is the best table i could find that includes one of the CaCl2 compounds.
See Table 1 The critical RH of 31% means that it starts to soak up water above that humidity. Below that RH, the compound stays dry. I dont know how different is the more common "anhydrous" variety. The uptake also increases with higher RH.
RH varies by season and across the county. Folks living in Tucson (dry) will likely have different in-house RH conditions than Atlanta (moist). Also, winter-time during the heating season is usually drier than summer. Even in a house, the RH can vary. The fish room will likely be the worst.

8. Originally Posted by Philosophos
Specific gravity would presume that it's a solid block of one of these nutrients. These are powders; plenty of air, static, moisture, etc. to deal with. These numbers are also the fertilator average; if you dig back through some threads you'll find that the maker (can't recall his screen name) just took mass consensus from APC as to their weight of a compound per cup and averaged. Some measured with their lab equipment, many with their kitchen measuring cups. Some had scales accurate to .001 of a gram, others had balancing scales accurate to 1 gram. Some people kept their bags at zero humidity and took out what they'd use in a short period of time, others had them in things like 80% relative humidity and opened them daily.

There's lots of room for error with fertilator, but so many use it that it's nice to have their conversion factors for dry dosing. It's also handy to check their numbers over. I put the values for some of the more common compounds above into a little spreadsheet just for checking over people's math who use fertilator but don't know how to make the calculations themselves. It's saved me countless hours of playing with a calculator.

Personally though, I just try to convert people over to at least using a scale to measure out daily values for dry dose. Stock solutions are pretty handy too.
Oh come the hell on............(jokingly).............you mean they do not measure down to the parts per billion and micromanage things with the upmost accuracy?
While poo pooing EI for it's "estmaition"?

Go on...........Do tell......

Then there's the issue of light which few seem to bother testing or measure, doing 10X worse than any estimation EI may do..........then CO2 which is really hard to measure.
It's practical management that is best suited for hobbyists' errors and habits.

Calculators are good for those who cannot do chemistry.
But as far as real usage, they are still very much "estimative".

Test kits in the hobby are also extremely prone to human habits(lack of calibration), thus are often just as bad in terms of "estimation" of a true datum.
But many claim they are still "required" even without calibration or with, and most of these blow hards that seem to poo poo EI for guessing, are doing no different.
They are still guessing and often with the same error.

No one has shown that EI fails in this regard.

I know Dan is well aware of this, but I wanted to make it very clear, there are many who think differently and want to use semantics, fuzzy words, dogma and ignore reality of the human factor as well as the observed facts.
Test kits are estimative as well.

They are close "guesses" with associated errors ranges.
That's how science works, same with mathmatical modeling that EI uses to guess the ranges also.

Any dosing calculator will also guess and estimate just like EI.
Perception plays a large role in how folks think and view these various models and methods.......but they all have the same traits.
As far as practical matters, all methods work pretty well horticulturally, so the need for more precision seems mute to argue.
Perhaps in some rare cases where you want to limit and ride ona razor's edge I suppose, but not otherwise.

If you think/believe so, you need to go back and convince yourself that is not the case.

Good points Dan.

Regards,
Tom Barr

9. Originally Posted by Neil Frank
The wt per tsp tables will be certainly be useful for administration of dry measures.

As mentioned previously, it is important to be mindful that many of the mentioned salts are hygroscopic, like calcium chloride Thus, the wt may vary by relative humidity and temperature.
This is the best table i could find that includes one of the CaCl2 compounds.
See Table 1 The critical RH of 31% means that it starts to soak up water above that humidity. Below that RH, the compound stays dry. I dont know how different is the more common "anhydrous" variety. The uptake also increases with higher RH.
RH varies by season and across the county. Folks living in Tucson (dry) will likely have different in-house RH conditions than Atlanta (moist). Also, winter-time during the heating season is usually drier than summer. Even in a house, the RH can vary. The fish room will likely be the worst.
Originally Posted by Neil Frank
The wt per tsp tables will be certainly be useful for administration of dry measures.

As mentioned previously, it is important to be mindful that many of the mentioned salts are hygroscopic, like calcium chloride Thus, the wt may vary by relative humidity and temperature.
This is the best table i could find that includes one of the CaCl2 compounds.
See Table 1 The critical RH of 31% means that it starts to soak up water above that humidity. Below that RH, the compound stays dry. I dont know how different is the more common "anhydrous" variety. The uptake also increases with higher RH.
RH varies by season and across the county. Folks living in Tucson (dry) will likely have different in-house RH conditions than Atlanta (moist). Also, winter-time during the heating season is usually drier than summer. Even in a house, the RH can vary. The fish room will likely be the worst.
But what of the theories held so dearly about the K+ Ca++ testing and dosing of some?
hahaha

Most aquarist have pretty high humidity in their homes where the salts are stored.
Mine are sealed, but the difference is less meaningful to me since it's estimative and non limiting. So while true, offers little practical difference, bu does add error to dosing calculators and test kit users.
It also makes a good size difference if you use those same salts to make up the calibration known reference solutions, if you are off there, then all the data will be skewed.

Bummer.............but we shall conveniently ignore that

Regards,
Tom Barr

10. Dan, I can offer up some Fe gluconate dry estimations for the teaspoons also for you.

Also, some EDDHA Fe 138 sequestrene.

I do a run of 20 samples and then send a error range associated(max/ min + mean is the reported).
I can do a error bar etc, but that would be best done using all the nutrient salts on a graph(this would be nice, but would require data entry for say 10-20 measures of each salt, then run a histogram with Y error bars).

Since it's estimative and for the hobby, the max/min + mean is a good range.

Regards,
Tom Barr

Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•