You don't dilute the coffee at all! Or brew a tea really strong! I'll use 20 or more teabags of the strongest stuff & cheapest stuff I can find and then spike it with powdered caffiene you can get at the health food store (gym rats use it just before their work outs). pour it thru the medea. I grow my cyms outside and every couple of months I'll unpot and check for newly hatched slugs. I almost always find a few. I'll pick them out, checking for any unhatched eggs along the way. It is the ongoing battle! DEATH TO SLUGS!!