This is my never-ending quandary and I'm about to try variations of everything I have learned over the past years, having experienced the problem several times. I normally try to ignore the little critturs unless they are gnawing on my plants but when I found an ants' nest inside the wormery, that was just a step too far!
Read more here about the various methods being deployed in Frugaldom gardens to deter the pesky wee beasties and then feel free to suggest any other alternatives you may be aware of or have tried with success. I do have some ‘Flour Helvas’ and am wondering if that could be used to good effect if I mixed it with baking powder.
One extra tip re the baking powder method – I keep an open tub with some in my fridge to adsorb odours, so I used it for the ants then replaced the fridge tub with fresh stuff. I call that frugal stock rotation. … Read more here