Q. Dear Umbra,

I’ve been doing spring cleaning and wondering what people who’d like to stay as green as possible use to keep the limescale out of their toilet bowls. Literally every product I’ve ever found (bleaches, cistern blocks, etc.) says somewhere on it “this product is harmful to marine life,” and that’s a deal-breaker for me. But I don’t want a toilet full of ugly, grey, smelly limescale. Suggestions welcome!

London, U.K.

A. Dearest Ros,