Feeding Flies To Fish?

As long as it's not dead because you blasted it with flyspray, I can't think of any reason why not.

Thanks, both.

Having spent yesterday evening pondering about whether there was any possibility that the flies had died of consumption of soap or cleaning products elsewhere in the flat, and therefore might pose a hazard after all, I then discovered that they've been wiped up this morning. There are a few living ones around, though, so I expect the fish will still get their chance of a natural meal in due course...