combining N/P/K liquid solutions

[growitnow]

Hello,

I have mixed separate liquid solutions of N/P/K. I add 5ml of the N solution and 5 ml of the P solution, plus 10ml of the K solution each time I dose (based on what ppm I want each solution to add at the time I dose).

Can I just dump the three three separate liquid solutions into one container, then add 20ml of the combined solution each time I dose?

Or does the math get more tricky when computing what a composite solution is adding.

thanks,

[Gerryd]

Hi,

I think you should be good to go.

I combine my dry N and P together with water, stir/shake, and serve.

I remember reading here that there are some other nutrients that should NOT be combined as they will be affected adversely (not chelate properly?) and that they should be dosed separately.

I will see if I can find it and post the link.

[VaughnH]

You can mix all of the nutrients except for mixing iron and phosphates together. Those two will combine to form an insoluble precipitate removing the iron from the liquid solution.

[detlef]

I'd really like to know how Tropica solved this issue for their plant nutrition plus liquid which contains not only a mix of micro elements including iron but also N, P and K.

Any body having a clue or should I better ask Tropica and get no answer?
Anyhow, I just ask out of curiosity.

Best regards,
Detlef

[Gerryd]

Vaughn

You can mix all of the nutrients except for mixing iron and phosphates together. Those two will combine to form an insoluble precipitate removing the iron from the liquid solution.

Thanks I thought Iron was involved, but couldn't find the thread right away..Didn't want to state incorrectly.

Detlef,

Any body having a clue or should I better ask Tropica and get no answer?

I don't have a clue either (probably the chemical called 'Marketing'), but I would be interested if they give you an answer, or non-answer as the case may be.

[VaughnH]

I will happily pose as an expert on this: (I will be off on an Alaskan cruise starting tomorrow, so that qualifies me.) Tropica uses a compound of iron that will not react with phosphates, so they have no problem.

[ceg4048]

See JamesC's data on this regarding the iron chelators. James' Planted Tank - All In One Solution

Evidently, the addition of Vitamin C keeps the solution acidic enough to stabilize the chelators in the trace mix to keep the iron away from the PO4.

Based on this he has developed a DIY TPN+ which works quite well.

Cheers,

[Tom Barr]

It depends on the chelator type and the concentrations of each nutrient, Fe and PO4.

You would need a rather strong chelator to keep it in solution, even if you add absorbic acid, this will not do much once you add it to the tank.

The strong chelator is the key there.

Trade off there: not particularly bioavailable Fe...........

But last a long time.

Regards,
Tom Barr

[growitnow]

My initial intention reveals my ignorance. After playing around with Gadd calculator, I realize the answer is "no, you cannot simply add the three pre-mixed solutions together, then dose 20ml".

The combining of solutes is not the problem. I (now, obiously) see to compute ppm per volume dose (add 5ml solution each dose, add 10ml solution each dose, etc.), one needs to compute ppm per dose, based on total starting volume for the combined solution (if mixing up 1000ml, for example).

So, in 1500ml distilled water I added:
75g KNO3
18g KH2PO4
150g K2S04

for 20gal tank, each +10ml dose should add
+0.4ppm nitrate
+1.1ppm phosphate
+8.4ppm potassium (from both sources)

Look right?

Any basis for using deionoized over distilled water? Distilled is easier to get in grocery store.

[ceg4048]

It depends on the chelator type and the concentrations of each nutrient, Fe and PO4.

You would need a rather strong chelator to keep it in solution, even if you add absorbic acid, this will not do much once you add it to the tank.

The strong chelator is the key there.

Trade off there: not particularly bioavailable Fe...........

But last a long time.

Regards,
Tom Barr

Hmm..OK, so how does Tropica accomplish this in their TPN+? Is it via a very strong chelator as you mentioned?

So, in 1500ml distilled water I added:
75g KNO3
18g KH2PO4
150g K2S04

for 20gal tank, each +10ml dose should add
+0.4ppm nitrate
+1.1ppm phosphate
+8.4ppm potassium (from both sources)

Look right?

Any basis for using deionoized over distilled water? Distilled is easier to get in grocery store.

Things can get more complicated that really necessary. Actually, there is no need to add K2SO4 since you get enough K just from the KNO3 and KH2PO4, assuming you dose the proper weekly levels of these two.

It's also not really necessary to use distilled water. Just use tap. The dosing levels are an estimate so there is no need for extreme accuracy and life is therefore made much easier. Check the UKAPS dosing guide for another point of view=> Welcome To The UK Aquatic Plant Society - The Estimative Index (EI)

Cheers,