That is a good question. Aquarium Salt in the water when you do a water change I'm told Will Kill Outdoors flowers. I have a betta in QT for fin rot and have been putting aqua salt in his water. I water my flowers with the old fish tank water outside and I did notice the plants did not seem to like the aqua salt. I'm guessing the same would hold true for aquarium plants. I think only the plants that can survive brackish would thrive in a tank w/ aqua salt. I took some of my java moss from my FW tank and added it to my bettas QT tank. It's been doing fine.