gH for plants and Fish

[Mav17]

Hi,

I am looking for a ratio of calcium, magnesium and potassium for use in Aquarium maintainence.

I am running a fish room and do not wish to add sodium chloride as i want to either add it in some circumstances (goldfish and tropicals) and not in others (plants, discus, systems with non salt tolerant species)

can anyone give me a recipe for ratios of required ions such as (but not limited to if more are required, except for sodium chloride) calcium, potassium, magnesium for proper osmoregulation of fish?

Thanks in Advance

 

[Mav17]

Any Takers?

Thinking further about this subject, i am assuming that fish wouldnt need as much potassium as a planted tank, but would still need some.

The general ration of calcium to magnesium seems to be 3:1. in planted tanks the potassium levels in a gH booster seem to be the same amount as calcium, so potassium, calcium magnesium ratios would be 3:3:1.

Reducing the potassium ratio in just a fish Aquarium would therefore be sensible, or at least logical.

Can anyone re-enforce my clarity here?

 

[pepetj]

I think there are more than one correct answer to your question(s). I use individual filtration systems in all my tanks even in my fishroom, if you are going to have tanks with different water parameter needs then consider setting separate reservoirs for feeding the targeted tanks by turns (e.g. soft/acidic versus hard/alkaline)-

I reconstitute RO water with Seachem's Equilibrium and sodium bicarbonate; no need to use NaCl as a source of Na. I don't use tap water at all (unsafe in my City).

Magnesium and Calcium levels as low as 3.5 to 4dGH have caused no problems in my soft acidic planted tanks. Potassium, on the other hand I would relate more to Nitrogen and Phosphorus than any other variable.

I suggest you browse the Newsletters published here. You may find what you're looking for and then some... (my experience here).

Pepetj
Santo Domingo

 

[Mav17]

ok so, i cant get into the newsletters, it is not letting me, i dont know what is going on there.

But i am thinking that the extra potassium is not a huge issue.

But i am thinking of using calcium chloride in place of calcium sulphate.

So, my next question is, what amounts of calcium chloride, potassium sulfate and magnesium sulfate do i use to get a 3:3:1 ratio of calcium, potassium and magnesium ions in the water?

 

[Cyclesafe]

You can't get into the newsletters because you need to be a subscriber. $12 USD, probably $6 AUS by now, is very well worth it.

Chemistry! I can help.

Molecular weights:

CaCl2 = 111 (36% Ca by weight)
K2SO4 = 174 (44.8% K by weight)
MgSO4.7H2O = 246 (9.8% Mg by weight)

3:3:1 Ca:K:Mg by ion would be 201g CaCl2 : 161g K2SO4 : 246g MgSO4.7H2O

 

[Mav17]

Thats Awesome cyclesafe, thanks Bud, much appreciated.

I think i might just suscribe too, but for now im off to work.

G

 

[Mav17]

Differing information and calculation

Hi Cyclesafe,

I haveing some issues finding Potassium Sulphate so i have settled for using potassium chloride.

However, upon searching for % by weight information on this i found some differing information to what you have provided in your last post.

If you follow the link below and type in for instance calcium chloride, or magnesium sulphate and the % by weight is different to what you have stated.

Is each chemical different depending on the supplier in regards to the percent by weight of the Ions in each?

And if so, then i will need to know how you worked out the amount of chemical needed to get the ratio from the previous post, can you provide the working and explaination for this please?

G

 

[nipat]

There are different types of "Magnesium Sulphate".
The difference is the amount of water in it.

The one we use most is Epsom Salt or Magnesium Sulphate Heptahydrate (MgSO4.7H2O).

Not sure about CaCl2, can you provide the source of that conflicting info?
So we can know what they are talking about.

 

[Cyclesafe]

Oooppps!!!

Back to school for me! I corrected the entries in post #5 above. Calcium chloride is CaCl2, not CaCl. And I had a typo in the gram value for K2SO4. I have confirmed these (revised) numbers.

Other than minor impurities, chemicals are the same regardless of supplier. The tricky part here, however is that MgSO4 is most commonly available as Epsom Salt, the heptahydrate salt of MgSO4. Anhydrous MgSO4 is available as a reagent, but would be a waste to use because it's going into aqueous solution anyway.

Molecular weight of KCl is 74.5 or 52.3% K. The relevant ratios 3:3:1 Ca:K:Mg would be:

201g CaCl2 : 138g KCl : 246g MgSO4.7H2O

 

[Mav17]

Hi Cyclesafe,

Can you provide the equation for working out these values, i assume i need to ask the supplier which form of magnesium sulphate it is, but of course, if it is only $30 for a 25kG bag then i assume it is hyptahydrate.

I would like to understand how the molecular weight is used to calculate the amount of the certain ion that is delivered in a mix so if i want to change a core ingredient, or change a ratio, i can.

Thanks

G

 

[Cyclesafe]

Sorry, but to understand this and to do what you'd like, you'll need to know some chemistry.

http://www.chemcollective.org/tutorials.php

Do the tutorial entitled "Stoichiometry".

Alternatively, if you are not interested in the details you can use this calculator:

http://www.aquaticplantcentral.com/forumapc/fertilator.php

 

[Mav17]

Hi Cyclesafe,

the info you have provided is very helpful, thankyou very much.

So, i have worked the ratios i need. But i am just wondering how this relates to a gH test with a test kit.

Using the fertilator i have input for a 100 liter Aquarium, that using 2gms of KCL, 2.9gmsCACL2 and 3.5gmMGSO4, that i will be getting 10.49ppm potassium, 10.47ppmCa and 3.45ppm magnesium.

so when i mix this all together, i would add a total of 24.41 grams of powder per 100 liters of water to get these values yes?

But, what will this increase the gH by, do i add just the calcium and magnesium values in ppm together get what the gH will rise by in ppm?

 

[Cyclesafe]

2.0+2.9+3.5=8.4, how do you get 24.41?

GH measures all divalent cations, primarily Ca and Mg, as ppm CaCO3.


GH (ppm CaCO3) = Calcium hardness (ppm CaCO3) + Magnesium hardness (ppm CaCO3)
GH (ppm CaCO3) = 2.5 x Calcium (ppm) + 4.1 x Magnesium (ppm)

2.5 x 10.47 + 4.1 x 3.45 = 26.18 + 14.15 -> 40 ppm GH

The coefficients are derived from the relative stoichiometries of the Ca and Mg carbonate salts..

 

[Mav17]

opps, was adding together the ppm values instead of the weights of the salts i was using.

Im a little confused however, because the fertilator said i would be achiveing 10.49ppm potassium, 10.47ppmCa and 3.45ppm magnesium when using 2gms of KCL, 2.9gmsCACL2 and 3.5gmMGSO4.

or is this a case of, yes these are the amount of the individual ions present when dosing, however when reading on the test kit as general hardness as CaC03 the rise in general hardness is higher because is it measuring the carbonate salt of these ions and not the ion itself?

Thanks so much for your help.

G

 

[Tom Barr]

Contact Dave Wilson in Darwin, he's active in the Clubs in Oz, Also Leo in Brisbane ought to direct you, quite a few folks there, also Singapore often will ship to OZ.

KICL is fine to use though.

For most fish/shrimp etc, TDS is likely a better parameter vs GH testing.
For some species like Rift fish, the SO4, K+, are quite high, so less on Ca and Mg..........

KH is another matter, I would watch this more and then use a small meter to test the TDS and add more GH booster(or your own DIY version) to top off to the ideal TDS.

 

[Tom Barr]

Here's the forum in Oz, these guys/gals will be able to help you out.
http://www.aquariumlife.com.au/forum.php

 

[Mav17]

Hi Tom,

I came here to get the best advice, and cyslesafe is helping me with that, just need to clarify the few small points in my last post in regards to the amount of ions added as per the fertilator, and what is being tested on a gH test kit.

As a matter of interest, gH is a better parameter to more than TDS. As TDS is the number of total dissolved solids in the water body that have electrical current measured by an electronic meter, there is no way to know what is in your water when measuring TDS, and i want to know that the three most important ions (calcium, magnesium and potassium) are there in the right numbers and at the right ppm level, before i go adding anything else.

I can then increase TDS as i need to with sodium chloride, if i even want to, which i dont necessarily need to if calcium, magnesium and potassium are there in the right numbers.

Again TDS is NOT a good measurement to use, because it uses a conversion factor to convert the conductivity reading to TDS, the raw reading is conductivity, which is a better reading to use because what you see is what you get.

In hydroponics there is a set conversion factor to convert the mS or uS conductivity reading to ppm TDS, many studies have been done on this and a conversion factor for hydroponics has been determined and manufacturers or fertilizers state the TDS that will be achieved when dosing their fertilizer nutrient into a hydroponic system. Because each aquarium is different, there is no way of knowing what conversion factor to use, therefore your readings can be MASSIVELY inaccurate.

Also, a TDS measurement/level recommended by one person, may be different to what another person is reading, because the TDS factors they are using on their monitors are different.

Then you go into the calibration solutions used for the TDS monitors, giving different conversion factors for each different calibration solution standard using different salts for the same ppm value.

For instance, a 300ppm TDS calibration solution using NACL might use a conversion factor of .55, a 300ppm TDS calibration solution using KCL might use a conversion factor of .72, a TDS calibration solution in using 442 (40% sodium chloride, 40% potassium chloride and 20% sodium bicarbonate from memory) might use a conversion factor of .62.

So even the calibration solution you use, even if you change the the conversion factor back after the calibration, will produce a widely varied result compared to another monitor using a different calibration solution.

so TDS is a very inaccurate and widely variable measurement that has no place being used in Aquaria because there is no set conversion factor to be used (considering every water body in every aquarium is different) and because of the different calibration solutions available that make each reading massively different for the same body of water depending on which one you use.

So, to save me repeating this whole thread on another forum, i might just wait until cyclesafe replys to my message, or anyone else who may be able to help me with my question. after all i dont really think it matters that im asking this question on a US forum from Australia as all our goals are the same yes?

G

 

[Cyclesafe]

You're understanding of GH and the concentration of Ca and Mg is correct.

Since GH measures Ca and Mg (and other bivalents) as if they were CaCO3, you need to figure out the weight conversion of Ca++ and Mg++ (as measured by, for example, the Fertilator) to CaCO3. For Ca, you multiply by 2.5 to get its contribution to GH (on a molecular weight basis CaCO3 is 40/100 Ca; inverse is 2.5). For Mg, you multiply by 4.1 to get its contribution to GH (on a molecular weight basis CaCO3 is 24/100 Mg - if Mg were substituted for Ca; inverse is 4.1).

 

[Mav17]

Hi Cyclesafe,

Thanks for that buddy. i now understand.

It would interesting to see how a magnesium, calcium and potassium test kit, for instance for marine aquariums (if they were compatible with freshwater) would react to testing these items and if it would be more accurate.

I might just experiment with that.

Again thanks for that mate, you have been extremely helpful.