According to the NOP all those things have a status of "Allowed" in organic food production, except certain iron chelates...
(Not all chelating agents are the same...EDTA, EDHHA, DTPA etc...and the rules here in Europe can be slightly different for certain things. Some are allowed, others are not. OMRI lists some chelates as "Not Allowed" while others are missing from the list with no data available. Neither Allowed, nor Not Allowed.
european guidelines and a lot of european organic status awards are most definately questionable, i wouldnt hold them in much higher regard than your own if im honest.
Regular maxicrop liquid actually isn't ORMI listed.
It is questionable as to if Maxicrop plus Iron is an effective way to add iron, see some of Vlads discussion on the topic.
The biggest question is why are you aiming for Organic? If you want to be able to claim "orgainc" or label things organic then you want to stick to things that are allowed or ORMI listed.
If you are just trying to be healthy about it that is different but there will be some things you may have to make judgement calls on or you might have to do some experimentation of your own to figure out how to do it.
Chelated iron, Vlad has done much research here so I'll defer to him. I know to an extent on use of chelated iron in organic production, certain things are only allowed when tissue analysis of the plants shows a deficiency and the only way to cure it is the use of the thing in question. For my only personal or not Organic certified use, when the plants show a need, I'll use an appropriate chelated iron product.
Potassium Bicarbonate: NOP considers it a synthetic and it is only allowed for plant disease control (not as a fertilizer.) There are some ORMI listed products with the main ingredient being potassium bicarbonate but most of them also contain surfactants and other ingredients so I wouldn't feel comfortable about using them as buffers in my aquaponics. I get food grade Potassium Bicarbonate from wine making supply places for use in my aquaponics for buffering when I need potassium. I don't know if this could be an approved use of potassium bicarbonate as far as the NOP is concerned.
Hydrated Lime: calcium hydroxide, Strong, caustic. It is what UVI and some of the other big (non organic) aquaponic operations use for keeping the pH up (they alternate between calcium hydroxide and potassium hydroxide) I've heard rumor that this would not be allowed for Organic production. But does that make it less safe to eat the food? I don't know but I kinda doubt it.
Potash Lye: potassium hydroxide, Strong, caustic. It is what UVI and some of the other big (non organic) aquaponic operations use for keeping the pH up (they alternate between calcium hydroxide and potassium hydroxide) I've heard rumor that this would not be allowed for Organic production. But does that make it less safe to eat the food? I don't know but I kinda doubt it.
Calcium Carbonate: Limestone, Marble chips (marble is simply limestone that is hard enough to take a polish.) shells, coral sand, chicken grit, hard water from a limestone aquifer, garden lime. I'm pretty sure this one can be counted as organic.
There might perhaps be a way to use hardwood ashes to make your own version of potash lye, potassium hydroxide, and perhaps even some extra processing to make it into potassium bicarbonate. However figuring out exact dosing and processing is going to be highly variable so you will be on you own figuring it out with only vague hints from even others who do it themselves.
Potassium bicarbonate is used by winemakers to raise the pH of their wine (or the terminology they use "lower the acid content"...which amounts to the same thing...raising pH), much the same way it's used to raise the pH of your AP system water. So wineries don't use it as a "nutrient" the way Aquapons do...In an AP scenario, potassium bicarb can serve 3 separate duties:
1) Added to system water to raise pH (and has the effect of adding some potassium)
2) Foliar fed as a fungicide (and should has the effect of adding some potassium, though I'm not sure exactly how effective this method alone would be...I'm not saying it's not, just that IDK)
3) Foliar fed as a potassium supplement (and has the effect of being an organic fungicide).
So, it's a fungicide, it's a K supplement, and it's a carbonate buffer.
As far as "synthetic" or "natural" to me, is as synthetic or natural as baking soda (NaHCO3) is... (potassium bicarb is also used as a dietary supplement for us humans)...
The term "organic" even when used in chemistry seems pretty arbitrary and is not always clearly defined, nor do the lines drawn make much sense sometimes. The use of the term by governmental regulating agencies both on this side of the pond and yours, make even less sense at times, is full of seeming contradictions, and even more arbitrary...
Allisyn, you can get a Tetra Test pH test kit at many aquarium shops for a couple bucks, they go down to pH5.0...really though I wouldn't even wait long for a new test kit as it might be too late...with your API test kit, pH6 is a big time red flag to take some action and buffer pH up...
No the plants would LOVE a pH 'well' below 6, it's your bio-filter that wont dig it. Like TC explained (we seem to have 2 threads going on at once on the topic)...
If your bio-filter starts to crash, you should see an ammonia spike...personally I wouldn't wait. But since you haven't ever buffered before and dont know how much of what to add to raise your pH slowly (0.2 to 0.4 units per day or so), and you don't know where your pH is really at, doing something at this point is going to be a touchy feel-y kind of affair because of the fish...Raising pH too quickly will stress them...Anything you might do, or at least anything I can think of, is going to involve a bit of guess work...and is not ideal
Though if I were in your shoes and I had to...I'd do something like take a 5 gallon bucket of top up water and see how much lime, baking soda or KHCO3 (whatever I had immediately on hand) it would take to raise pH 0.4 units. Multiply that amount by 20 (I think you said your system holds about 110 gallons, right?), dissolve it in a bucket and add it to the system as a "First AID Emergency kind of band-aid" measure pH in 3 or 4 hours...Then tomorrow I'd cut that amount in half and add it to the system again, and measure pH again hoping to see something above 6...And hopefully by that time I would have gotten a hold of a pH test kit that can measure below 6...I'd keep buffering 0.2 or so units per 24 hours...
If anyone sees anything wrong with this idea...please advise. Seems better than waiting for your system to crash...
And I wouldn't make a habit out of ever doing something like that again :) (not knowing where my pH was at). Also, topping up with as much "hard" water as you can at this point might help too...
Yeah, that's a pretty good conclusion (about the top-ups with city water). I don't have an API test kit but I think TC, Nate Story and other folks mentioned that basically at or anywhere below 6 the color is the same.
Really you don't need a Tetra Test brand kit, but those are the one of the ones I happen to use and know they go down to 5. Any decent brand will do.
The hardness in tap water in many places is enough to keep the pH from dropping too low. But it is best to know where it is.
I like my pH on the API regular pH test to read green. My well water is so hard, I rarely get to see that though. Wish I had the gutters hooked to my rain water tanks for all that lovely rain we just had.