Coffee Grinds

[Ric.ror]

Would coffee grinds applied to the surface of my indoor plants stop the dreaded house flies from laying their eggs?

[Redhelen72]

Not necessarily and it may affect the acidity of the soil
If you cover the surface of the compost with a 1cm-thick mulch of gravel, grit or ornamental glass pebbles, this will stop house plant flies from being able to lay their eggs.

[ladybirder]

Wouldn't it be better to stop the house flies getting into your home in the first place Ric.ror? I hate them and have fly screens at patio doors and windows.

https://www.amazon.co.uk/Window-Door-Fly-Screens/s?k=Window+and+Door+Fly+Screens

[Old_Geezer]

No harm in trying, but I'd not hold my breath were I you.

(I feel sure flies can get in from the soil you used to fill the pot.)

[Ric.ror]

Thanks for your answers everyone

[Chipchopper]

Spent coffee grounds may control slugs, to some extent, in the garden.
You may find yellow sticky labels good for those tiny fungus flies