I have recently added a compost bin to my garden, and now I have a plague of ants marching around my garden to the compost bin, and then back to two places.

I have read that you actually only generally see 5% of the ants and not the whole number of the colony at anyone time. This means that I have a large number in my garden!!

Other than getting rid of my compost bin (which I really don't want to do), how can I deter them? I only have a small garden and while they don't bother me now, I worry they might invade my house (they are rapidly growing in number). A toxic pesticide is an option I would like to refrain from as I understand that ants are a vital part of the ecosystem and can often be friendly helpers. But if they insist of scaring my fiance out of the garden they'll have to go.

I have narrowed them down to pest ants, not carpenter ants. Any advice please?