Fert weights confusion

[Nick potts]

Hi all.

Looking to clear up some confusion over my fert weights and dosing.

I am using the APF starter kit and mixing as per there instruction (4tsp KNO3, 1tsp KH2PO4 and 6tsp of MGSO4), now according to the IFC calculator the APF provides 14.7ppm NO3, 4.2ppm of PO4 and 7.3ppm of Mag per week, i have been wanting to up my levels to closer to full EI on the KNO3, CA, MG and K, so got a recipe ready and weighed all the powders out.

Now the issue i have is that according to the calculators i should be adding less ferts to my dosing bottle than i was before?? Is this just a miscalculation on the IFC sheet or am i missing something? @Zeus.

For example i want to target around 25ppm KNO3, which should be 17gram in 500ml with a 10ml dose x3 per week, this is about 2 teaspoons and before i was adding 4, I am unable to get any nitrate reading at all in the tank and seeing some deficiencies i think, hence why i am upping it (I know about test kits being rubbish )

Cheers

 

[Nick potts]

Anyone?

 

[arcturus]

What is the volume of water that you are adding the fertilizers to? And while you wait for a reply from one of the experts, I would double check the calculations. One teaspoon equals 4-6 grams (e.g one teaspoon of sugar is ~4 grams). So I seriously doubt that 2 tsp of KNO3 can weigh 17g.

 

[Ria95]

17g KNO3 in 500mL solution with a dose of 10mL 3 x per week will add 25mg/L NO3 to a 25L aquarium.
I think you can adjust the dosage to your tank volume based on that.

Teaspoons are not used to measure mass/weight, scales are. It's as nonsensical as saying I added 2mL KNO3 salt. I think that is all there is to this calculator tsp vs that calculator tsp or a shop tsp.

 

[Zeus.]

IFC calculator the APF provides 14.7ppm NO3, 4.2ppm of PO4 and 7.3ppm of Mag per week

These figures was based on each teaspoon weighing 6grams, which its doesn't, But it is close enough, try not to get tied up with exact weights to reach perfect ppms, because there isn't a perfect ppm for all tanks. We are aiming for ferts in abundance that's all. If you think your not dosing enough just dose 10-50% extra for 4 to 6 weeks and see if it helps, if it does and you added 50% extra cut back to 25% extra wait 4 - 6weeks if plants look worse up it again a bit. As long as ferts are in abundance and regular WC (water changes) all is good fert wise.
If you double your fert dose then and there is no improvement, its not ferts and think CO2 if injecting, flow (even in low tech tanks) and the all important maintenance of filter and detritus build up in tank.

I use the IFC for each batch of ferts I make - but rarely do I get the mass spot on eg add 46.5grams of Potassium Nitrate it will be 47+ grams or if a bit sloppy it might even be 50grams, I don't start again for that batch there will be just a little extra abundance of NO3 It doesn't need to be rocket science or spot on

I do take more care when/if making custom trace mixes - but even then with serial dilutions it will make little difference as long as the mass of salt is close (or just over) what is needed.

What we was after in giving APFUK ppms is so for folk could dose at those levels with bespoke doing volumes eg dosing 6 ml every day is a pain IMO, if we can dose say 10ml or 100ml daily life is easy esp if you want to dose say 10% extra it so easy.

Plus we also wanted the APFUK ppms so folk could compare it with other regimes or products so folk could easily see it is great valve for money with little effort/equipment

 

[Nick potts]

Thanks all.

What is the volume of water that you are adding the fertilizers to? And while you wait for a reply from one of the experts, I would double check the calculations. One teaspoon equals 4-6 grams (e.g one teaspoon of sugar is ~4 grams). So I seriously doubt that 2 tsp of KNO3 can weigh 17g.

I will crack out the scales and measuring spoons later (yes i am bored with nothing else to do lol)

But it is close enough, try not to get tied up with exact weights to reach perfect ppms, because there isn't a perfect ppm for all tanks. We are aiming for ferts in abundance that's all.

I use the IFC for each batch of ferts I make - but rarely do I get the mass spot on eg add 46.5grams of Potassium Nitrate it will be 47+ grams or if a bit sloppy it might even be 50grams, I don't start again for that batch there will be just a little extra abundance of NO3 It doesn't need to be rocket science or spot on

Yes, I agree and I would also round up and even then not overly precisely.

Plus we also wanted the APFUK ppms so folk could compare it with other regimes or products so folk could easily see it is great valve for money with little effort/equipment

This is what got me, I was comparing full EI with the APFUK and it just didn't add up with the calcs, I will do it again later (see above about being bored )

 

[Nick potts]

OK, so I just weighed out what I normally add in KNO3, 4tsps equals 28grams according to my scales (they are freshly calibrated) which would be 41ppm per week and is quite a bit more than the 20grams I am supposed to add for full EI levels.

So I should be registering some nitrate in my tank water surely?

 

[Zeus.]

OK, so I just weighed out what I normally add in KNO3, 4tsps equals 28grams according to my scales (they are freshly calibrated) which would be 41ppm per week and is quite a bit more than the 20grams I am supposed to add for full EI levels.

Whats-
Size of tank?
Fert contaner size ?
Dosing frequency ?
Dose amount ?
I will run a double check

So I should be registering some nitrate in my tank water surely?

Well I never check, if we are adding the salts that's what we have added, there should be no need to check as they are in abundance. Testing is so hit and miss. Plus if dosing macros three times a week the plants may be using a good proportion daily so it may never show much, also the substrate may also be mopping up the NO3 quite quickly so that would also get a lower NO3 reading. Once the nutrients are bonded to the substrate plants can easily still get there hands on it all the same.

 

[Nick potts]

Whats-
Size of tank?
Fert contaner size ?
Dosing frequency ?
Dose amount ?
I will run a double check



Well I never check, if we are adding the salts that's what we have added, there should be no need to check as they are in abundance. Testing is so hit and miss. Plus if dosing macros three times a week the plants may be using a good proportion daily so it may never show much, also the substrate may also be mopping up the NO3 quite quickly so that would also get a lower NO3 reading. Once the nutrients are bonded to the substrate plants can easily still get there hands on it all the same.

Thanks Zeus.

Tank is around 25-30ltrs (39ltrs gross), quite a bit of soil and hardscape
500ml container
10ml per dose
3 doses a week.

 

[Ria95]

So I should be registering some nitrate in my tank water surely?

Very likely the test kit went bad. It can happen even within the expiration date especially if opened for a long time in humid conditions.

Try a strong positive control by your fertilizer in a small volume ( 1ml in 1L would be 21mg/L NO3 with the 17g KNO3 solution) to see if you get the expected color change.

 

[dw1305]

Hi all,

I will crack out the scales and measuring spoons later (yes i am bored with nothing else to do lol)

It depends on crystal size etc. but as a general rule the salts of heavier elements are denser.

As an example sodium (Na) element 11, RAM - 23 and chlorine (Cl) element 17 RAM = 35.5 form a salt, sodium chloride (NaCl) with a density of 2.16 g/cm3, but go down a level in the <"periodic table"> and potassium iodide (KI) has a density of 3.13 g/cm3.

cheers Darrel

 

[Zeus.]

Tank is around 25-30ltrs (39ltrs gross), quite a bit of soil and hardscape

I always use the gross size so for 39 litres

If you call it 25 litres

So its between 26-42 ppm NO3 So Full EI in my books, The actual value is irrelevant as long as NO3 is in abundance all the time.

 

[John q]

@Nick potts forget the fancy calculations, for the above mentioned weights and ratios you're adding roughly.

Element	ppm/degree
NO3	34.34
N	7.76
K	21.66

Now the salts could be bad... are you seeing any nitrate related deficiencies, if not then ignore the test kit.

Caveat. IFC calculator will differ slightly with above reading's..