Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Depends on how well stuck the crud is, but it is almost always alkaline minerals or salts, so acidic cleaners to soak and wipe will work best. If the lid is slightly damp (most lids in use will be) then a quick wipe might be enough.
For an older lid that has been in storage, and the minerals and salts are caked on use something more aggressive, and perhaps repeated soak-and-scrape sessions.
Citric acid, lemon juice, vinegar, CLR and so on.
Soaking a paper towel and holding it on the hardest crusts is a good way to work them loose. Alternate with a razor.