Flourish Phosphate - calculation error?

1459 Views 6 Replies 2 Participants Last post by ^iMp^, Dec 20, 2004

^iMp^

Discussion Starter · Dec 15, 2004

The fertilator is giving me the following:

Tank size: 15g
Product: Flourish Phosphorus
Amount: 2 mL (NOT teaspoons)

Calculate -> Phosphate increase of 1.59 ppm Phosphate

===============

According to the bottle, 2 mL into 15 gallons should yield: 2/(0.8*15) = 1/6 ppm Phosphate. Now...I could be doing something completely boneheaded, but I don't think it's THAT early in the morning.

Sorry if this was pointed out already...

^iMp^

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MicB

· #2 · Dec 17, 2004

O.K. Bonehead(your choice of words)
Your only defense is if you are American
This is metric so make it a decimal
Not 100% sure of the problem you are having but
1/6ppm is not the end result
1 divided by 6 = .16666666ppm

Working the other way

.8 x 15 x 1ppm(max recommended) = ml
12 x 1 =12ml

or

.8 x 15 x .15ppm(min recommended) = ml
12 x .15 =ml
1.8ml

If NASA scientists are so bright why do they count backwards?

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^iMp^

Discussion Starter · #3 · Dec 17, 2004

MicB said:
O.K. Bonehead(your choice of words)
Your only defense is if you are American
This is metric so make it a decimal
Not 100% sure of the problem you are having but
1/6ppm is not the end result
1 divided by 6 = .16666666ppm

Wait...since when is it wrong to express rational metric numbers?

MicB said:
Working the other way

.8 x 15 x 1ppm(max recommended) = ml
12 x 1 =12ml

or

.8 x 15 x .15ppm(min recommended) = ml
12 x .15 =ml
1.8ml

Ok...then reversing my calculation:

.8 x 15 x .1666666 ppm = 2 mL

Then reversing the fertilator calculation:

.8 x 15 x 1.59 ppm = 19.08 mL

So something is screwy...or it's been WAY too long since I've had a math class.

^iMp^

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MicB

· #4 · Dec 17, 2004

You still have trouble somewhere.
Can you state exactly what the problem is. Give your statement/calculation and the correct? calculation so we can compare the two and see the problem.
Thanks

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^iMp^

Discussion Starter · #5 · Dec 19, 2004

MicB said:
You still have trouble somewhere.
Can you state exactly what the problem is. Give your statement/calculation and the correct? calculation so we can compare the two and see the problem.
Thanks

Ok...

The Flourish Phosphorus bottle has the following formula: 0.8*v*p = m, where...
v = the volume of the tank in US gallons
p = the desired phosphate increase (ppm)
m = the amount of Flourish Phosphorus to use (mL)

Using the fertilator's calculated Phosphate increase (1.59 ppm) in the 15 gallon tank:

m = 0.8*15*1.59 = 19.08 mL (clearly different than the 2 mL I put into the Fertilator to get the 1.59 ppm result) So this is the error.

What should 2mL yield? 0.8*v*p = m -> p = m / (0.8*v)

So... p = 2 / (0.8*15) = 1/6 = .166666... ppm. This is the correct answer, which the fertilator does not produce (it produces the aforementioned 1.59 ppm increase).

^iMp^

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MicB

· #6 · Dec 19, 2004

Oh O.K.

1.59 looks very close to .16 if you have a decimal in the wrong place. Is there no written errors in your test kit ppm values. What is the range of your test kit and does the colour fall approx in the right area for 1.6 or .16 colour range.

Did you test your Phosphates before you started. I. e. was the tank 0 phosphates to start with. Some supplies have high phosphates to start with . Test you water supply

Use your water change bucket and add some phos by cal to bring up to .15 and see if it goes to 1.59 again. Should be only very little amount.
Test first there is no phosphate in the water supply.

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^iMp^

Discussion Starter · #7 · Dec 20, 2004

MicB said:
Oh O.K.

1.59 looks very close to .16 if you have a decimal in the wrong place. Is there no written errors in your test kit ppm values. What is the range of your test kit and does the colour fall approx in the right area for 1.6 or .16 colour range.

Did you test your Phosphates before you started. I. e. was the tank 0 phosphates to start with. Some supplies have high phosphates to start with . Test you water supply

Use your water change bucket and add some phos by cal to bring up to .15 and see if it goes to 1.59 again. Should be only very little amount.
Test first there is no phosphate in the water supply.

Not off by a decimal place. I know (from past experience) that 2 mL of Flourish Phosphorus does NOT raise 15 gallons to 1.59 ppm.

Look at your own first post. You gave a result of 12 mL to raise 15 gallons by 1 ppm. The fertilator says that 2 mL will raise it by 1.59 ppm! No possible, according to both of our calculations.

^iMp^

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