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Just a note, the PPS-Pro site could use a revision imho. I am very impressed with everything you are trying to do, and have been looking through your site carefully due to my intention to switch to dry ferts for my aquarium. Here is one question I have, under the R/O section, you state:

How much CaSO4?
The recommended level is 20 - 30 ppm and can be dosed after water change or once a month. Plants need very small amounts of Calcium but it has to be available in full concentration.
41 gram / 100 gallon -> 30 ppm
11 gram / 100 litre -> 30 ppm

Then if you skip down two questions, you get this:

Is Magnesium to Calcium ratio important?
No. Plants don't care about ratios.

I think given all the talk about the correct balance of nutrients being essential in our trace element mix, we need to talk about why, and while I assume the law of the minimum, (if a plant needs a certain element for a particular metabolic function, such as Ca or Mg, and is unable to obtain enough of it, then it will display a deficiency and will not grow properly or at least to its full potential), plays a role, however I am more familiar with how terrestrial plants work. Therefore I am curious what you have to say about this, as I am a little confused. Don't get me wrong, I really like the idea of what you're doing, but the lack of the "why" or "how come this works" that I see on your website is something that could be addressed. Personally, I had never heard of this system until very recently, but have been running two tanks essentially as low-tech PPS tanks for almost two years where I have allowed the vegetation to take care of the fertilization, the invertebrate and microfauna to grow, and have kept the feeding and fertilization to a minimum. However, I do use products such as Mosura's Old Sea Mud Powder and Shi Zhen to add minerals I feel my shrimp, (and fish, and crayfish, and plants, etc.,) benefit from. I wish I knew more about the exact breakdown of these products, but I don't, but due to their outrageous pricetags, I am going to be switching to dry ferts where applicable, and regardless of whether I am taking care of a rare succulent, an emersed Crypt, a submerged eco-system, perhaps with riparian vegetation, perhaps an epiphytic orchid or something of that nature, or outdoor plants, I want to give my plants the best care within reason, (reason meaning both dollar signs and I want to minimize damage to the environment).

At any rate, I am not criticizing your method except for the "plants don't care about ratios" statement. That is just something that I think needs to be expounded on. Perhaps in this case, with aquatic plants, they will take the calcium they need from the water, and if it is slightly harder they won't mind, I'm not sure, I'm not a wetlands expert, and I'm too sleepy to think right now, but juts wanted to point this out as it seemed like a clear contradiction to me.
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