topless nano. How does it effect water quality?

[Salty_Box_Reef]

Other than the fact that Ill get more water evaporation, how does not having a top on the tank effect the water quality? I had a glass top made for my biocube, but I'm getting tired of cleaning it, and also like to be able to see in from the top, but I'm wondering how it will effect water chemistry vs having it covered?

 

[MitchReef]

Evaporation is the only real effect I can think of unless there is a chance of something accidentally getting into the tank or fish jumping out of the tank....most people don't put hard lids on their tanks because it severely restricts oxygen transfer...