Oh, yeah. Reishi is...uh...like, the ambient spirit pressure in the air? Where hollows, and Arrancar live, Hueco Mundo, has a lot of it. Or, well, so he tells me.
Anyway, he's used to having plenty of it in the air, and here? Not very much.
So, I've been...er...feeding him.

And, it's true, you know. You're really nice to everyone, and always taking care of people. You should let them take care of you, for a change, heh.