iann wrote:Any concentrated acid is dangerous. Concentrated (or glacial) acetic acid is highly corrosive and just the fumes will damage your lungs. Glacial acetic acid is fairly widely available although you won't run across it by accident. Mineral acids tend to be found more often in concentrated form and less often in dilute form because there is little use for the diluted forms. So people have developed the idea that they are "dangerous" while acids such as acetic and citric are "safe".
Citric acid is actually stronger than acetic acid, also triprotic, but it is less commonly available in concentrated form. Citric acid is useful for making buffers because of the dissociation constants of its second and third protons. In the diluted forms you're likely to find, both acetic acid and citric acid are safe, edible even There is some speculation that the acetates produced after neutralisation of hard water by acetic acid can be helpful in transport of nutrients into plants. Citric acid would presumably do the same, it is widely used as a chelating agent in cleaning, although I haven't seen anything written about it relating to plants. The two are closely linked chemically and both citrates and acetates occur in natural (animal) metabolic cycles that also involve lactic acid.
Should've qualified my comment on citric acid with the word "dilute". Since I haven't had the need for anything other than 5% vinegar, I'll stick with that as the safest recommendation for using it in acidifying hard water. I'll leave the subject of concentrated acids up to people who know how to handle them properly. By the way, thanks much for what you said about the speculation concerning byproducts of acetic and citric acids in nutrient transport for plants -- very interesting!
osac wrote:Have to find ammonium sulphate , but will go without it for now. I know that fish in aquarium secrete amonium and that plants love that but not sure that it is ammonium sulphate but it could be.
So when I get aquarium will use that water instead of distilled maybe.
Except that ... it's winter and not sure about using fertilizer now, maybe just once as I did not use it at all and than just watering without fert. during winter.
So... is it a good plan or I missed something.
I believe your cacti are dormant now. That means no growth in the winter, so they shouldn't be getting watered or fertilized until they're ready to grow again in spring. I've heard that people use aquarium water for whatever nutrients are in it, but in my opinion that's not the best way because you'll have no way of knowing if your plants are getting enough or too much Nitrogen. As Ian and I said, Ammonium sulfate should be easily available at garden supply stores, although maybe not so easy to find in Croatia? (I'd be surprised if that's the case!) Not an urgent matter for you at the moment, and hopefully you'll be able to find it either locally or online.