Alfredshouse is gone.....

[Myka]

You can put your lids back on once you get a skimmer. I have had lids on some of my tanks (with skimmers) with no troubles. Help keep evaporation down as you already know. Now that you have an O2 kit, you can always test just to make sure!

Expensive lesson to learn, but you can scratch that one off the list on newbie mistakes now.