Rohrer and Klingner Scabiosa is a German ink that comes in a 50ml bottle. It's popular for two reasons, the first being that it's water resistant since it is iron gall, just like Salix. Check out what Wikipedia has to say about it, but know that this ink is not the same 'pure' iron gall that is known to be corrosive to metals, rather it is a modern formulation that behaves much more like conventional fountain pen ink. Rohrer and Klingner does recommend that you clean the ink out of your pen every week, and be aware that iron gall inks aren't ideal for all pen types and models.
Scabiosa's water resistance and ease of cleaning are every bit as great as Salix. There is one aspect where Scabiosa has a leg up on Salix, and that's dry time. Salix had about a 25 second dry time, but Scabiosa dries quite a bit faster, only about 10 seconds on Rhodia paper, which is quite ink resistant. This is a huge plus given that it's a pretty wet writing ink. And the shading is great, too!
Check out the other Rohrer and Klingner reviews I've done:
You can find Rohrer and Klingner Scabiosa in a 50ml bottle available at GouletPens.com for $11.95 or as a 2ml sample for $1.25.
If you've used Scabiosa before, I'd love to hear what you think in the comments below!