Do you have too many slugs in your compost bin?
In a spray bottle, mix in 1 cup ammonia to one quart water. Go out at night and spray slugs wherever you find them. Ammonia will have no affect whatsoever on your compost. It will only kill slugs and snails. If you go slug hunting in daylight, check under rocks, pots and lids, any dark moist hiding place. You can somewhat trap them by placing said hiding places in proximity to the bin.
Even though slugs contribute to decomposition, they tend to stray from the bin into the garden. Many people find this unsavory, so if you have too many slugs, fill up your ammonia sprayer and take it to ’em.