Aquaponic Gardening

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I am in the process of getting our aquaponic system certified organic. But I have run across some hurdles that I need help with.

I was using calcium carbonate/potassium carbonate to raise the ph of my system, however potassium carbonate is not allowed.

I was thinking of using Espoma GL6 Garden Lime Soil Amendment, which consists of pelletized dolomitic limestone.

Question 1:

Has anybody had any experience with this stuff or is there something else I should use to raise ph?

I also discovered that the chelated iron I was using from the aquaponic source is synthetic and for the most part cannot be used for organic certification.

Question 2:

What type of iron are people using for organic aquaponics? And what ph do I have to keep my system at to make it available to the plants?

Question 3:

I found this stuff: Monterey Dr. Iron which is omri certified, has anybody used it for aquaponics?

It's always nerve racking when switching inputs so any advice from you fine folks would be much appreciated.

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I would recommend reading the Friendly Aquaponics newsletters on the subject because they have covered it really well (and are organically certified so you know that their Certifiers have approved the method which makes it easier to go to your Certifier with an example of it being approved). Scroll down about half way and look for Newsletter #27- 29ish "Organic Aquaponics Systems" and #34-35 are commercial pH related.

Hi Max. You could also try... On the upper right on the home page type in what you want to search aquaponic gardening and see what comes up. This site has a lot of info.

I assumed he already tried that Jack =) It is rough going through the certification process so I just shared my best resource for a 'strait from the source' knowledge bank. Best of luck getting certified, it is a huge accomplishment Max!


Thanks Jess & Jack, I have looked at the friendlies newsletter, and I will go back and reread, but usually what I found was that they used an organic calcium carbonate and iron, but never specifically state where to find them or what brand/manufacturer.

As for searching this site, I have tried, but again there is nothing specific mentioned, just stating that you can't use the synthetic chelates. But I am also terrible at internetting. It took me way too long to figure out how to sign up for this site :)

I was hoping some one had a brand or a source that they can point me to. As I mentioned above, I am really scared to try out new products without some input from other people.

Especially the iron, since it is really ph dependent.

Since Calcium Carbonate is on the OMRI Generic Materials List you do not have to use a specific brand. I get my Calcium Carbonate from the feed store in a 50lb bag- They call it Oyster Shell and carry it in crushed or flour form. I prefer the crushed because it just sits in the system until it gets used, I put it in a mesh bag. In the OMRI Generic Materials book in the crop section look at Calcium Carbonate, its class CF, non synthetic and allowed. It specifically list options including Oyster Shell.

Your Certifier should be able to help guide you on this type of thing. I would check that your certifier is one of the few who have already certified an aquaponics system. May be less fuss for you if they already are familiar and have their ducks in a row so to speak.


You can use potassium bicarbonate as a foliar spray to control powdery mildew which will supply potassium to the plants as well. I have heard of it used in combination with worm tea. It is difficult to control PH with just calcium carbonate alone as it is slow acting making it difficult to respond to PH swings.

How large is your farm going to be? If you are going to sell at farmers markets and not wholesale or grocery stores then Organic might be a hassle that you don't need. If you have a one on one relationship with customer you can make the point that aquaponic is better than organic. This is Green Acres business model - you should study what they do.

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