Covering tank?

Would it be a bad idea to place a piece of plexi glass approximately 1 inch above the water level on my aquarium. It would not cover the entire width of the tank and barely the length. How would this affect the system?
What would be the pros and cons?

 

Pros: less water evaporation, less fish suicide bombers
Cons: Less gas exchange, less gas exchange, trapped heat, less light shining through, constantly having to clean the salt creep off to help light go through, and most importantly less gas exchange.

I wouldnt do it. Taking my glass cover off my tank has been the best cheapest thing i have done for the tank.

 

Only thing i can add to what he said ... Is if you have cats that like to get up top and go scuba diving I would cover it...

 

sweet... wont do it then. I just hate the large evaporation rate.

 

Well if you want to prevent animals entering or exiting, then use a fitted piece of egg crate...