These prices are ridiculous for a bit of calcium nitrate. I buy that stuff at a MUCH lower price per kg, while for Magnesium, I use Epsom salt.

hmm i never thought about making my own.
what would the recipe be for making something similar to cal-mag?

Can't find any info about what exactly is in Cal-Mag, apart from Calcium, Magnesium and Iron. It also sounds very concentrated, as they advise using 1-2 tsp per gallon of nutrient.

Why - exactly - did you use it, and . . . did you find it usefull?

Greystoke,
Most cal-mag products use Calcium nitrate, Magnesium nitrate, and iron edta. (ie nothing special)
Here`s a typical analysis
Total Nitrogen (N)ÂÂÂÂÂ2.0%
1.94% Nitrate Nitrogen
0.06% Water Soluble Organic Nitrogen
Calcium (Ca)ÂÂÂÂÂÂÂ..3.2%
Magnesium (Mg)ÂÂÂÂÂÂ1.2%
Iron (Fe)ÂÂÂÂÂÂÂÂÂ...0.1%

Thanks Hex. Indeed, nothing special.
And that must cost $21 per litre! What a rip-off!

Based on that analyses, you would need:
Ca-nitrate (tetra-hydrate): 188 gram/L for 3.2% Ca
Mg-nitrate(hexa-hydrate): 127 gram/L for 1.2% Mg
FeEDTA @ 15.21% Fe: 6.5 gram/L for 0.1% Fe
(but IÂm getting a level of 16% for NO3 ???)

Hi Greystoke,
No clue why how they got their figures but its cheap :)
Maybe using MgO and CaO would be a better option?

Don't know. Perhaps they're only using a bit of ca/mg-nitrates, mixed with other (cheaper) salts. Perhaps acetates. I think I could formulate something like that.

Anyway, I think chinamon has enough info to start his own concoction.

Good luck, and let us know.

I came across this info which may (or may not) be useful, i lost the link but there were no accurate liquid or material measurements mentioned so you`ll have to play it by ear,it appears to be 50/50 by volume from the description :)

2 liter jug plastic and added 2-3 cups of that (Florida Crushed Coral Substrate) it filled the jar to about 4 inches. Put plain old white vinegar (5%) over the media til about 4 inches above the coral.

6 hours after adding white vinegar to the crushed coral,
its still bubbling alittle
PH is coming up slowly now 5.2
mag 164 mg/l or PPM
and calcium is 11808 mg/l

@ hex2006,
You can do the same thing with pulverized magnesium carbonate (magnesite, dolomite as in natural mineral form) but using citric acid instead, to dilute and extract magnesium, plus some Ca, and rare trace elements (Co and Ni "contaminations" in millimols). A strict disclosure agreement doesn't permit me to release further details, though. ;-)

PS: do not forget to cook both 'soups' to be sure to fully eliminating the acids...

Thanks for that Lucas. Happy New Year!
I have some surplus 99% pure calcium carbonate powder gathering dust in the cupboard from my lizard keeping days.
How much powder should i dissolve in 500ml of white vinegar(5%)and what ppm of calcium would the resulting concentrate provide if diluted at 1ml/L?

Looks like my New Years resolution is to do more experimenting with homebrew nutrients :)

Happy new year to you too hex2006!
As for calcium I can tell (as it has already been posted here previously): with 5% vinegar you always get 15000 mg/l or ppm, as this is the "max saturation" that this acid concentration can dissolve from natural source in 1 liter. You (only) need 60-70 gram (playing safe) per Liter to get the max (15 gram) of dissolved Ca as acetate in the solution.

Were you confusing calcium carbonate with magnesium cabonate? Anyways, as I said I can't (am not allowed to) tell about how much ppm of Mg will be dissolved out of MgCO3 trough a specific concentration of citric acid. But perhaps someone else can tell or determinate.

Hi Lucas
Sorry for the confusion,itend to go off on a tangent sometimes :)
I figured it would be more useful to have some calcium acetate in the cupboard than a tub of calcium carbonate.
So it appears 30-35g should be enough for 1/2 litre. I guess i boil it up after dissolves to remove the acid and then make it back up to 1/2 litre using ro water.

I put 40g of powder in a jug and poured a 568ml bottle of white vinegar in. It instantly started to froth but luckily didn`t make it to the top. I gave it a good old stir and left it for 8 hours to do its thing.
The reaction now appears to be over (no bubbles)and the excess powder has settled out to maybe 1/8" thick on the bottom so it looks like i might be needing some more vinegar.

A quick calc tells me that 24.1 gram of pure Ca-carbonate will dissolve in 568mL of 5% vinegar.
Assuming that your powder contained 36 gram of pure carbonate, then you could add another 280mL of vinegar to dissolve the lot.

Question:
1. Does the same thing apply when using 5% citric aid, which is actually cheaper when made from citric acid powder.

Remark: the idea of dissolving both calcium carbonate and magnesium cabonate in either acid is to get some sort of "Cal-Mag" substitute. Both components mentioned earlier as Calcium Nitrate and Magnesium Sulfate (Epson S.) are fine to supply Mg and Ca in a standard NS, but they come with two downturns 1. they deliver N and S in considerable amounts, not only Ca and Mg. 2. You can't mix the nitrate and sulfate in one concentrate (but need to use it in 2 components). Otherwise, a chemical reaction with irreversible Ca precipitation (out of calcium nitrate) is the inevitable consequence.

So, if you want to produce a real "Cal-Mag substitute" you need to go for dissolving your Mg from magnesium cabonate with citric acid (suppose it works with 5% vinager too).

The trouble I've found with dolomite (which is a double salt of Calcium and Magnesium carbonate) is that it is not easy to extract the Magnesium. You can dissolve the calcium part easily in pool acid, which leaves you with raw Magnesium carbonate, but that is reported to dissolve only in 20% Sulfuric acid at ± 90°C after about 3 - 4 hours.

Haven't tried this with citric acid.

Thanks Greystoke,
I`ll pick up another bottle of vinegar and let you know what happens.