Moon -- There are plenty of non-corrosive fluids that can be used as tire ballast. I use the "animal safe" antifreeze as I have five dogs, several cats, etc. Others use windshield washer fluid. Neither will damage your rims one bit.
I live in the Green Mountains of northern Vermont. Very hilly, with some wicked slopes. I couldn't believe the difference in stability the loaded tires made, especially with FEL work. Traversing a slope with a full bucket held really low, hit a small bump, and before ballasting my tires I had more than my share of "pucker" moments when that uphill tire seemed like it wanted to ease up into the air. Now, everything stays on the ground where it's supposed to be.
The only downside from my perspective is that those filled tires are gawd-awful heavy if you ever have to change one out.
Pete (geek)
Clementine (L3010HST)