it will get better gas exchange being open, but should not pose a problem
with it mostly covered so long as it has a way to exchange air into and out
of the canopy. do you have a sump to allow the gas exchange there?

kc

"Slim Shaggy" wrote in message
...
if i put a glass top on my aquarium about 1/4" above the water level will
it
hinder the gas exchange? It won't cover the whole top, I need about 2" at
the back for the wires and hoses and such..

my water surface is pretty turbulant, but I'm wondering if having the
glass
so close affects the amount of oxygen available to the water..

thanks.
ss