Aquaponic Gardening

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Has anyone utilized General Hydroponics CALiMAGic (calcium, magnesium, chelated iron) as a supplement in an AP system? Pictures of the bottle attached below.

Thank you!

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I am familiar with that product, but I don't use it in aquaponics because of the nitrogen content (one of the ingredients is magnesium nitrate hexahydrate and is found in quantities of 10% to 30%)

Botanicare's Cal-Mag product contains even more nitrogen.

My systems have plenty of nitrogen which are produced by the fish, so I don't want to be adding more. Too much nitrogen is not a good thing.

I think just recently Sylvia was testing out some different Cal-Mag products and found that they jacked up the nitrogen content of her system(s) beyond what she deemed to be good.

Thanks for the help Vlad! I have an IBC setup in a hydroponic shop that I work at. Our nitrogen ppm's are on the low side. CaliMAGic is the only chemical we currently have in stock that could possibly help with Ca-Mag deficiencies/ won't affect pH drastically. I was thinking about adding half of the recommended dose, but my greatest concern is for the fish. 

I'm not a big fan of using standard hydroponic nutrients in AP systems, as most of the time they are not appropriate.

The magnesium content of magnesium nitrate hexahydrate is 9.478%

The amount of nitrogen is 10.93% (as total N)...

 30ppm of Mg is a generic "standard" amount accepted that most plants, in most phases of growth will do well with. (Like most things in hydro, this is a bit you are right to cut that in half)...

If you cut that to 15ppm of Mg (using that product as your Mg source), you can expect to raise N by slightly more than that. But even the above is impossible to calculate because the company lists "between 10% and 30% magnesium nitrate present in that bottle...make sense? There's a big difference between 10% and 30%.

Things like that are only part of why hydroponic products aren't really advisable for AP.

Go to the local grocery store and get yourself some Epsom salt. It is 9.98% magnesium by weight. It is not the most ideal Mg salt for AP, but is certainly harmless...and somewhat widely used in AP...

...and it contains a known quantity of Mg (Epsom salt is magnesium sulfate don't forget to count those 7 molecules of water if you are working out molecular weight to percentage ratios).

About 16 grams of epsom salt per 26 US gallons should get you to 15ppm Mg. (that figure 16 grams is somewhat adjusted for common impurities)...

And you won't have to wonder about how your fish will fare 


Actually, I've been meaning to ask you Vlad...what do you consider to be some ideal Mg salts for aquaponics?

I did a little research and Kelp4less has a cal-mag organic product which their representative told me contained no nitrogen (as opposed to their other cal mag products which did contain nitrogen). That might be worth looking into :)

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