I'd make a fence out of grounds. The caffeine in the grounds is what kills the slugs. So if you put a line of defence around the bed, you should be alright. I'm not sure that grounds sprinkled over the bed will be adequate.

Try for something thats sharp like ground up egg shells or sharp sand. I have snail problems in my potted bulbs from time to time and removing of any litter first followed with an irritant seems to work best.
The coffee grounds are great for acid loving plants by the way.
Mike

Hmmmm. Slugs eat coffee grounds around here! As for the caffeine....studies have shown that a spray made out of a very high percentage of caffeine kills slugs, and there are probably commercial products out there. But you can't brew it up yourself, strong enough, that is.

I suspect if your slugs are repelled by coffee grounds, it is because they don't like the feel of them. There is really nothing in the grounds that would repell them. I wonder if you are talking about fresh coffee grounds and not used????

Another myth about coffee grounds is that they have an acid reaction......and they don't! Much of the acid in coffee ends up in your cup and is leached from the grounds. Coffee grounds are basically neutral, but still an excellent addition to the compost pile. Worms love 'em!

Hi all, here's my slightly embarrassing newbie follow up. I assumed I had snails munching away. I was wrong. When I unrolled some shade cloth that I had not been using, out jumped all the earwigs! I have been getting about 80 per night with beer traps for about 5 nights now. I get a slug or two as well.