I don't believe any of the water conditioners marketed by the major aquatic supply companies contain anything that could harm any aquatic plant or animal you might keep in your aquarium. But if you're planning on adding a Nerite snail to your aquarium, be prepared for the white spots (Nerite eggs) all over your aquascape. I had three at one time and regretted adding them when the eggs began to appear on my dark driftwood; I find it very distracting and unappealing. I don't think I would mind it as much if there was a chance of them hatching and growing, but since I don't have a brackish water tank, there's no chance of that. However, although I'm not positive, I don't think that Nerite snails are hermephrodites, or if they are, I suspect they need to be fertilized by a second Nerite before they can lay eggs, because now that I am down to just one Nerite, I have seen no more eggs, indicating to me that I either have a male, or else (hermephroditic or not) they need to mate with a second snail before they can lay eggs. So maybe you won't have that problem with just one Nerite snail, but perhaps someone else knows more about them and can elaborate.