I don't know. I kinda like the look of the grape caulerpa. I know that it is going to get annoying, but I figure that I could just rip it out every few weeks. I have a friend that would like the algae, so I could just give it to him. He only has flourescent, but I figure that if I give him a ton of this stuff, some of it may survive.
Yes, the scraper rusts like crazy. I used a metal blade to clean the tank the first time, and then next day I found it all rusty. I would only use them once. I have heard of getting 100's of these, but I am not sure on the cost. Right now, I have ran out of metal blades, and I am using a plastic one that honestly doesn't do anything.
Oh, and I have a question: Do blue legged hermit crabs molt, or not? I saw one of mine kinda dead, but I am not sure if that's just it's exoskeleton.