paperfish

Thanks for all the hard work! Really makes something so daunting seem almost easy to a newb like me

Not sure if i missed the feature, but if Fertilator could calculate a Target ppm for each chemical according to Tank Volume, or its not as simple as that

Thanks!

EDGE

The Fertilator should be updated with other chemical make up such as Calcium Nitrate 15.5 (/w ammonium), Magnesium Nitrate, Ammonium base product, Calcium Sulphate, etc.

darkoon

Great tool, any reason that GH booster has not been included in the calculator? also maybe add a column for tap water information, which is available from local DEP water report.

Oreo

I have noticed what I believe are errors in the calculations.

When selecting the volume of the aquarium it shows the units as gallons, however the calculation seems to be using Liters.

For example, when I add 10g of KNO3 to my 82gal aquarium it raises the nitrate level about 5.2 ppm (actual / measured) but this fertilator says it should raise the ppm 19.8 ppm. If I multiply my 82gal x 3.79 (the conversion factor from gallons to liters) = 310L. Using 310 as the volume (in "US gallons") the fertilator gives me 5.2ppm, exactly what I measured.

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Further still, when I select the Liters unit the calculations are off by another 3.79x. Using the same numbers from above, ( 82gal = 310L ) + 10g of KNO3 = 5.2ppm. However when I input 310L + 10g KNO3 it says I should get 19.8ppm, which is the same percentage error. The result should be exactly the same as above, 5.2ppm.

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Another calculation in question... The product I bought from GLA labeled "mono-potassium phosphate" gives me a measured .75ppm increase of phosphate in 82gal per .44g dose. This corresponds to the fertilator's calculation for "K2HPO4", which is actually Dipotassium phosphate. I'm not sure who's wrong, the Fertilator, or GLA but there's definitely a discrepancy here.

On a positive note, the US gallons function appears to be working correctly for this calculation.


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I'm not going to do UK gallons but I think those calculations, including calculations for each chemical are worth checking as well at this point.


Had me scratching my head on this for a while.

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For the record: I started into this trying to calculate the exact volume of water in my aquarium system (Considering concrete background, lower then normal water level, plumbing & filter volume, etc.) for more accurate fert dosing. I figured if I knew the dose size of a fert, and the before / after nutrient concentration I could work backward to find the exact water volume. But the calculations using the fertilator were wildly off from reasonable expectations & my own measurements. Once I figured out the errors above, 82gal clicked for both nitrate and PO4 calculations exactly in line with measured results. Further, I have a high degree of confidence in my measurements because I am using a quality milligram scale to measure dry fert doses, and a Hach DR2000 spectrophotometer to measure actual nutrient ppms in my aquarium water.

ray-the-pilot

The correct answer is 19.8 ppm of NO3-

10g KNO3 x 62g per moleNO3 / 101.1 g per mole KNO3 * 1/82 gal * 1/3.78L per gal *1000 mg per g = 19.8 mg/L = 19.8 ppm

Since you do not show any of your calculations it is not possible to say why you are wrong but maybe you are finding ppm's of N not ppm's of NO3. If you divide PPM's of NO3 by 4.4 you get ppm's of N. Post your calculations!

Oreo

I'm not doing calculations. I'm dosing & testing using high quality professional lab equipment. I'm a professional with nearly 10 years of water treatment experience.

The problems are simple programming errors. Someone started with liters, then forgot and labeled the pull down menu "gallons". That error got perpetuated for the calculation associated with the "liters" label in the pull down menu when the same formula was used for the "liters" calculation but multiplied by the 3.79 conversion factor. That explains why the "Liters" calculation is off by the same amount in the same direction. The "US Gallons" calculation is actually the correct "liters" calculation.

I'm not sure what's going on with the PO4 stuff. Like I said, it's possible GLA sold me mis-labeled fertilizer, but based on what I've seen already, my money is on the fertilator being programmed wrong on that too.

Jeffww

I thought ppm was parts-per-million in terms of mass (mg/L) since 1kg=1l of water.

If you're looking for PPM N. In one mole of KNO3 you have only 14.01g.

In 10g you have about 1/10 of the mass of N since the molar mass of KNO3 is 101.

So you can say in 10g of KNO3 you have 1.4g of N.

1400 mg/310L = 4.5ppm. These are all very rough estimates. I think the discrepancy is coming from the fact that there is a moles ppm and a mass ppm. The held convention in chemistry I believe is mass ppm.

Oreo

I'm not measuring N (nitrogen), I'm measuring NO3 (nitrate) ppm (mg/L) with the spectrophotometer. I'm also not measuring P (phosphorous), I'm measuring PO4 (phosphate) ppm (mg/L).

The measured concentrations I'm getting don't correspond "roughly" to the errors I've pointed out. They correspond EXACTLY. It's a predictable error. If I was getting numbers that didn't fit an easy pattern I wouldn't be so certain but in this case it's obvious.

If you want the fertilator to give correct nitrate results, enter your aquarium volume in liters but select "US gallons" in the fertilator. Doing that will give you the correct KNO3 dosage to ppms of nitrate calculation.

wet

Oreo,

But, you're aware ppm is mg/L and that the manual calculation by ray-the-pilot only makes the following assumptions:

1) The purity of the solute (KNO3)
2) The purity of fluid (water)
3) The solubility and rules of Chemistry

Since your very nice equipment is significantly (~400%) different from that calculation, you have to wonder about 1, or 2 (this includes, perhaps, your tank having flow such that the location of your sample has a lower concentration of NO3 ions relative to the rest of the tank, or the calibration of your scale, your estimate for water volume is way off, maybe that your plants are N limited and uptook super duper fast, a combination of some of any of that, or something else). Regardless, you should be calibrating the tools vs a known sample of RO/DI and KNO3. The steps ray took above is exactly how you'd calibrate vs the sample.

It is not a question of the niceness of the equipment. In this case, I'm gambling on the math because of assumption 3 above.

Oreo

I can dose a 1gal bottle of distilled water with a precisely measured quantity of KNO3 and then measure the PPM (mg/L) of nitrate using my photospectrometer. The measured PPM of NO3 will be EXACTLY what the fertilator says it should be if the volume of water was 3.79gal. (1gal = 3.79 liters) The calculation is off by the conversion factor from gallons to liters.

I don't know what else to say here guys. Test it for yourself & see.