no more air wont hurt the plant water temp will determine usable amounts of oxygen in the res
yes water can leak out if you made holes in the buckets or totes for fittings below the waterline
the other thing is if the water is high enough in the res and the air bubbles splash enough it will form drips on the lid
depending on the angles of the lid the water can make its way to the edge once its on the edge it can easily leak out
I cut old top portions of buckets to attach to my lids to make kind of a skirt has to be top portion of the bucket, but under the immediate lips of the bucket (that is the very top of the bucket where the lips are is cut off and discarded you want the portion just under there cause its flat) that has to be cut off you can maybe get 2 skirts out of a bucket you don't want it too small
so basically some type of skirt close to the edge of the lid but not so close it interferes with opening and closing of container
the splashes that are on the lid reach the skirt and go back down instead of to the edge of the lid and onto your floor
something I figured out since I run my water fairly high compared to other people
when I fill and when I top off daily its about 1/2 inch up the bottom of the net pot so my lid gets constant splashes
from the air