A: If the storage is short term (up to 3 days) add nothing. The seal is such that the moisture will not escape. If you're taking them for a week or two all you need a few drops of distilled water in the green foam piece up top. Two rules of thumb. 1. never tap water (you'll get mold) 2. Herf-a-Dors are not made for long-term storage. Hope that helps.