Water in a Mother Flask

[Royal]

How much water or other liquid overlays is too much in a mother flask? The mother flasks are baby food jars with about 30 ml of medium. There is about 2 mm of sterile, distilled water on top of the seed in one flask. I used more water to get the last of the seed from my test tube, and wound up with about 2 cm of liquid on top of the media in flask #2. They are not vented, so I can't count on evaporation.

Anybody deal with this? What is the most water, disinfectant, nutrient overlay, or other liquid that anybody has been successful with?