A bit confused about fertilizer and ration

[tjatx]

Hello all,

I am in the process of setting up a new US 20 gallon tank and a bit confused about the fertilization process. I used to have a 200 gallon heavily planted tank couple of years ago and was using all in one fertilizer, but the cost added up quick. After some life changes, I am getting back into the hobby and starting small so the 20 gallon. I don't want to use all in one because of the cost so decided to go with dry salts and this is where I am getting a bit confused.

I am using the IFC calculator and I'm afraid it's a bit too advanced for my brain. If I am using KNO3, do I need to put the ratio as 100 next to the compound name? What's the solubility level?



I am also using the chihiros dosing pump so it can pump the fertilizer about 10 minutes before lights come on. Using 100% RODI water since my water is extremely hard. Should I make any changes to the fertilizer salts?

 

[hypnogogia]

Set the ratios to 1 for all your salts. The solubility level tells you how close you are to not being able to dissolve your salts in your chosen quantity of water.

Why are you using potassium sulfate? Why no magnesium? What are you doing for Fe?

 

[tjatx]

Thanks for your reply. Can you explain what do you mean by this? The solubility level tells you how close you are to not being able to discover your salts in your chosen quantity of water.

Using potassium sulfate because I have a bit left over for my garden project. I was thinking about buying some magnesium sulfate but, since I am using shrimp mineral gh+ to remineralize my water , assumed magnesium will come from that. For Fe, buying the GLA ETDA+DTPA micomix.

 

[hypnogogia]

Thanks for your reply. Can you explain what do you mean by this? The solubility level tells you how close you are to not being able to discover your salts in your chosen quantity of water.

Typo. Discover = dissolve.

Using potassium sulfate because I have a bit left over for my garden project. I was thinking about buying some magnesium sulfate but, since I am using shrimp mineral gh+ to remineralize my water , assumed magnesium will come from that. For Fe, buying the GLA ETDA+DTPA micomix.

Ok. You can also use the calculator to make your own remineraliser at a fraction of the cost.

What are your targets for NPK? Your ratio of K to N seems very high.

 

[tjatx]

I am not sure what my targets should be. 😕 Any recommendations?

Tried to clone APT sky and not sure about the ingredients to get. Should I go with magnesium chloride and calcium nitrate? Should've paid more attention to chemistry when I was in school. 😀

 

[dw1305]

..... Tried to clone APT sky and not sure about the ingredients to get. Should I go with magnesium chloride and calcium nitrate? .....

That would be a mix which you could use as a solution, because all <"nitrate (NO3-) and chloride (Cl-)"> compounds <"are soluble">. People often use magnesium sulphate (MgSO4.7H2O) and calcium chloride (CaCl2.2H2O), but you need to dry dose these, because calcium sulphate (CaSO4.2H2O) has limited solubility.

Fe alone won’t suffice as you need other micro nutrients, so ise CSM+B.

What @hypnogogia says, you need all fourteen of the <"essential plant nutrients">.

Cheers Darrel

 

[tjatx]

People often use magnesium sulphate (MgSO4.7H2O) and calcium chloride (CaCl2.2H2O), but you need to dry dose these, because calcium sulphate (CaSO4.2H2O) has limited solubility.

Thank you, dw1305. I am going to use this mix for my water.

Going back to the fertilizer question, should I just use KNO3 and KH2PO4 so I would have the NPK needed for the plants and then use Magnesium sulfate and calcium chloride for the RO water and that should do it? Just need to buy something for Fe. Since I will be using 100% RO water, is EDTA mix better than CSM+B?

Sorry for all the questions. I appreciate everyone's help. 🙂

 

[hypnogogia]

Going back to the fertilizer question, should I just use KNO3 and KH2PO4 so I would have the NPK needed for the plants and then use Magnesium sulfate and calcium chloride for the RO water and that should do it?

Yes, that will do it.

Just need to buy something for Fe. Since I will be using 100% RO water, is EDTA mix better than CSM+B?

Fe alone won’t suffice as you need other micro nutrients, so use CSM+B.

 

[tjatx]

Fe alone won’t suffice as you need other micro nutrients, so use CSM+B.

Thank you very much.. Is it true that I shouldn't dose macro and micro the same day? I guess something about Fe binding with phosphates?

It was very easy when I had someone else do all the hard work. 🙂

 

[hypnogogia]

Is it true that I shouldn't dose macro and micro the same day? I guess something about Fe binding with phosphates?

You can dose them in the same day as long as you allow a little time between them. A dose macro and micro one hour apart using automatic dosers.

 

[tjatx]

I am even more confused now. Does this look correct? NPK ratio shows 7:1:21. Something seems off.



Also, I may have to buy new fertilizers. I had some KNO3 and K2SO4 unopened in the bag but, it was sitting in the garage without any ventilation for the past couple of years and since temperature can reach over 100°F in the summer, I think it may have gone bad?

 

[tjatx]

Perhaps I am overthinking this a bit and making it more confusing. I think if I stick with KNO3, KH2PO4 and K2SO4, that would cover the macros and it just need to figure out how soon I can get the CSM+B.

 

[tjatx]

Sorry, one last question. What's the main difference between CSM+B and EDTA+DTPA micromix? It seems both have the same ingredients? 😵

​

 

[dw1305]

Hi all,

People often use magnesium sulphate (MgSO4.7H2O) and calcium chloride (CaCl2.2H2O), but you need to dry dose these, because calcium sulphate (CaSO4.2H2O) has limited solubility.

I should have explained that bit as well - <"Cacl2 + MgSO4 in the same bottle ?">:

• "Epsom Salts" or magnesium sulphate heptahydrate (MgSO4.7H2O) go into solution as magnesium (Mg++) and sulphate (SO4--) ions.
• Calcium chloride (<"CaCl2.nH2O">) goes into solution as calcium (Ca++) and chloride (2 Cl-) ions.
• These ions will recombine in solution if one of the products is insoluble (or of very limited solubility),
• magnesium chloride (MgCl2.nH2O) isn't a problem, because the chloride containing compounds we are interested in are soluble, but
• calcium sulphate (CaSO4.2H2O) is of very limited solubility "CaSO4.2H2O 2.63 g/L (25 °C)" <"Calcium sulfate - Wikipedia"> - and will precipitate out as a solid salt
• We can reduce this risk by dry dosing straight into the tank, where dilution is our friend.

cheers Darrel

 

[dw1305]

Hi all,

Also, I may have to buy new fertilizers. I had some KNO3 and K2SO4 unopened in the bag but, it was sitting in the garage without any ventilation for the past couple of years and since temperature can reach over 100°F in the summer, I think it may have gone bad?

It should be fine, although possibly now in a solid lump? You can still chip some off and use it.

I think if I stick with KNO3, KH2PO4 and K2SO4, that would cover the macros

You are going to add a lot of potassium (K), you probably don't actually need the (di)potassium sulphate (K2SO4). The advantage of KNO3 and KHPO4 is that both the cation (K+) and anions (NO3-) and (PO4---) are plant nutrients. If you add 10 ppm NO3- (via KNO3), you also add 6.1 ppm K+, and if you add 2 ppm PO4--- (from KH2PO4) you've added another 1.7 ppm K+.

Does this look correct? NPK ratio shows 7:1:21. Something seems off.

No, it is 30 : 3 : 20 for NO3- : PO4--- : K+ (the green numbers) if you add six doses a week.

What's the main difference between CSM+B and EDTA+DTPA micromix

We have a thread <"Lean dosing pros and cons">.

cheers Darrel

 

[Happi]

Also, I may have to buy new fertilizers. I had some KNO3 and K2SO4 unopened in the bag but, it was sitting in the garage without any ventilation for the past couple of years and since temperature can reach over 100°F in the summer, I think it may have gone bad?

These listed chemicals should be safe to use as long as they've been kept dry

Perhaps I am overthinking this a bit and making it more confusing. I think if I stick with KNO3, KH2PO4 and K2SO4, that would cover the macros and it just need to figure out how soon I can get the CSM+B.

Sorry, one last question. What's the main difference between CSM+B and EDTA+DTPA micromix? It seems both have the same ingredients?

KNO₃, KH₂PO₄, and K₂SO₄ are all fine to use. For micronutrients and iron, I recommend the GLA version.

CSM+B contains EDTA-chelated iron, whereas the GLA version includes both EDTA and DTPA iron (also known as Plant-Prod Chelated Micronutrient). DTPA is a more effective form, especially if you have hard water.

 

[tjatx]

Hi Darrel,

Hi all,

I should have explained that bit as well - <"Cacl2 + MgSO4 in the same bottle ?">:

• "Epsom Salts" or magnesium sulphate heptahydrate (MgSO4.7H2O) go into solution as magnesium (Mg++) and sulphate (SO4--) ions.
• Calcium chloride (<"CaCl2.nH2O">) goes into solution as calcium (Ca++) and chloride (2 Cl-) ions.
• These ions will recombine in solution if one of the products is insoluble (or of very limited solubility),
• magnesium chloride (MgCl2.nH2O) isn't a problem, because the chloride containing compounds we are interested in are soluble, but
• calcium sulphate (CaSO4.2H2O) is of very limited solubility "CaSO4.2H2O 2.63 g/L (25 °C)" <"Calcium sulfate - Wikipedia"> - and will precipitate out as a solid salt
• We can reduce this risk by dry dosing straight into the tank, where dilution is our friend.

cheers Darrel

Thank you very much.. I am starting to understand it a lot better.
Wouldn't adding calcium chloride to aquarium water causes it to heat up and also create HCl which may cause ph to drop? I remember reading about it in Chem class many moons ago.

 

[tjatx]

These listed chemicals should be safe to use as long as they've been kept dry


KNO₃, KH₂PO₄, and K₂SO₄ are all fine to use. For micronutrients and iron, I recommend the GLA version.

CSM+B contains EDTA-chelated iron, whereas the GLA version includes both EDTA and DTPA iron (also known as Plant-Prod Chelated Micronutrient). DTPA is a more effective form, especially if you have hard water.

Thank you!! Off to GLA to buy the EDTA+DTPA micromix.

I sincerely appreciate everyone's help. I thought setting up a tank by myself was a daunting task but you guys are so helpful that I am ready to jump in without any hesitation. 😀

​

 

[Happi]

Wouldn't adding calcium chloride to aquarium water causes it to heat up and also create HCl which may cause ph to drop? I remember reading about it in Chem class many moons ago.

When calcium chloride (CaCl₂) dissolves in water, it releases calcium (Ca²⁺) and chloride (Cl⁻) ions. The process is slightly exothermic, meaning it gives off a bit of heat—but this is only noticeable when mixing it into a small amount of water. In a full aquarium, you won’t feel or see any temperature change from it.

To illustrate how CaCl₂ is formed: if you take a few grams of calcium carbonate (CaCO₃) and add it to 500 mL of water, it’ll mostly settle at the bottom because it doesn’t dissolve well on its own. If you then add a few milliliters of hydrochloric acid (HCl), you’ll get a reaction—bubbles will form as CO₂ gas is released, and eventually, you’ll be left with a clear solution. That solution now contains CaCl₂, and the HCl has been fully neutralized in the process.

However, if you added more HCl than necessary, the leftover solution would contain both CaCl₂ and unreacted HCl. That could absolutely lower the pH significantly if added to an aquarium. But this is not the case with commercially available CaCl₂, which is already neutral and doesn’t contain any excess HCl. That’s why it’s safe to use in aquariums, as long as it’s pure and properly dosed.

To clarify: CaCl₂ doesn’t create hydrochloric acid in your aquarium. Even though it’s made by reacting HCl with calcium hydroxide or calcium carbonate

Ca(OH)₂ + 2HCl → CaCl₂ + 2H₂O
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

—these reactions fully consume and neutralize the acid. So by the time you add CaCl₂ to your tank, there’s no acid left to lower the pH.

That said, adding fertilizers containing chloride or sulfate ions might cause a very slight drop in pH over time. But in a properly buffered aquarium, this effect is so minimal it’s usually undetectable.

Thank you!! Off to GLA to buy the EDTA+DTPA micromix.

I sincerely appreciate everyone's help. I thought setting up a tank by myself was a daunting task but you guys are so helpful that I am ready to jump in without any hesitation. 😀

​

We’ve got a fantastic community here at UKAPS, always ready to help out. Feel free to share your water parameters or any other details or questions you have— the more info you can give, the better we can assist you!

 

[Happi]

100% RODI water since my water is extremely hard. Should I make any changes to the fertilizer salts

I missed this earlier, but here are my recommended chemicals:

For Mineralization:

• CaCl₂
• CaSO₄
• MgSO₄

Macro nutrients:

• KNO₃
• KH₂PO₄
• Urea
• K₂SO₄ (optional, you can skip it if you prefer)

Micro nutrients:

• GLA EDTA + DTPA