Nope other than recycling water from a reef tank to a fish only tank, there really is no viable option for recycling saltwater. If you add it to your plants, it will "salt the earth" and make it useless for growing anything in the future.
The high ratio of waste water to good water is the main reason I stopped doing RODI (as well as the high quality tap water in Greater Vancouver). I do 110g+ water changes on all my tanks at the same time, which means I would need 6 to 8 barrels just to store the waste water for using in my garden in the summer.
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