Actually dandelions are a diuretic and it could be a poor plan to feed it to a uro in large quantities. I don't know about hibiscus specifically, but it's not unreasonable to be thoughtful or cautious about feeding huge quantities of something you haven't researched thoroughly.
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Torey
Eugene, Oregon, USA
1.1 Saharan Uros (Joe and Arthur)
3.0 Mali Uros (Spike, Turtle, and Tank)
1.1 Ornate Uros (Scuttlebutt and Shazzbot)
1.1 Collared Lizard (Ripcord and Rorschach)
2.0 Green Anoles (Bowser and Sprocket)
1.1 Chubby Housecats (Roscolux and Jenny)