> Sulfuric acid or nitric acid would have a more favorable effect on the nutrient profile, but they're more and much more dangerous respectively.
Sulfuric acid is not really that dangerous unless you are getting the high test stuff from a chemical supplier. You can use battery acid refill solution, it's just deionized water and H2SO4 at around 30% concentration. That's mild enough that it won't cause any immediate burns, but you should still wear gloves and goggles when handling it.
There's no need for nitric acid, since you are already supplying nitrate ions.
Yeah, battery acid is sometimes used, and not a terrible corrosive risk with the precautions you note. I don't love that it doesn't come with any specs e.g. on heavy metal contaminants, but I think it's near-certainly fine in practice. ACS grade would have specs, but I don't want to handle the concentrated acid.
Sulfuric acid would give me excess sulfate, but since the plants aren't too sensitive to that I expect that would be an improvement over my current excess phosphate. I'm not sure if I'd get calcium sulfate precipitation as the reservoir concentrated. Nitric acid would let me hit my target profile exactly (with a corresponding decrease in nitrate salts), but it's way more dangerous. I've seen nitric acid used in academic trials and in countries with weaker safety laws, but not commercially in the USA.
Yeah, it's annoying there is no purity spec on the battery acid, but in all likelihood, it's pretty pure. One could always test it.
I mean I bet nitric acid would work great for that purpose, it's just a bit more expensive and harder to get in some places, as you mention. It's definitely commercially available in the USA though.
Sulfuric acid is not really that dangerous unless you are getting the high test stuff from a chemical supplier. You can use battery acid refill solution, it's just deionized water and H2SO4 at around 30% concentration. That's mild enough that it won't cause any immediate burns, but you should still wear gloves and goggles when handling it.
There's no need for nitric acid, since you are already supplying nitrate ions.