I've always just given them ball lightning tribute
Helps to raise your civ level too!
It was getting a little crazy there while I had a blue node linked though, I was fighting off attacks like every few turns it felt like.
Also, the ice bat is really hard to see against the snow background on strategic map. Fortunately it has that turn warning thing, so I was able to deal with it, but without the warning I wouldn't have even noticed it.