What kind of anemone is it?
I'm glad that you've found it. Assuming it's a green BTA, being in a crevice is ideal. It'll expand when it's ready. Not much for you to do at this point. Just let it settle in.
Regarding parameters, typically reef tank parameters are fine. Again, assuming it's a BTA, it can tolerate quite a bit assuming it's healthy. You'll want to avoid huge swings in water parameters, including temperature. The addition of iodine is sometimes recommended, though I've done it in the past and haven't seen any conclusive results. And since we typically don't test for it, we don't know how much is in our water to begin with, so we don't know how much to add.
If you have powerheads, make sure that you have anemone guards, or you will eventually have a pureed anemone.