Red ants? I would scatter ground up orange peel on the soil.

Never heard of that, tugbrethil, might have to try it. Otherwise, Guest, turn the pots out and rescue the plants (you might have to wait a bit for the ants to run away), clean the pots, repot in fresh compost, stand the pots on something that lifts them clear of the surface beneath, either pot feet or bits of broken roof slate, or whatever. Dust surface beneath with ant powder.