Managed to catch one of the fry that were floating around the tank (I swear, all our fish are constantly pregnant. I think there's one male and four females and they're constantly dropping fry.) It's the first time we've actually been able to catch one, so after a brief stay in a Tupperware container it's now living in a shiny new breeder tank. It's tiny and transparent and adorable.
Also, Nobbers has taken to sleeping on his side. It's very cute: