Agree. The goal is to add only what the plants actually can use. I take the approach that caution is better than assumption. Water is continually entering the fish through every cell and at the gills. Substances dissolved in the water may or may not get through the cells (gills are another issue). It depends upon the size of the particles dissolved in the water, as large particles cannot diffuse through the cell membrane. I am not a chemist and I have no way of knowing the particle size in these products, and I suspect the manufacturers would never disclose such information--I once asked Seachem about the level of TDS in Prime and they came back with "no idea," which I took to mean either they really didn't know or more likely they did not want me to know. So caution (and common sense) tells me to avoid the risk. The gills issue is a bit different, as chemical substances in the water can impact their function; clarifiers for example will bind the gill filaments which in time starves the fish of oxygen, while chlorine burns the filaments, and aloe vera slowly destroys the filaments, and other substances can have similar effects.