Yup i tried it, it gets a messy foamy fermenting bubble feast on the top side, plants oxygen and other gasses released by the water. I tried to attach a hose in it about 0.5mm from the top to suck the gass out with a pump bubble by bubble while it forming. I did it with a litlle sqaure tank and inclined it towards the suction. I was surprised that even 3 cm incline wasn't enough to get all air to the highest point by itself. In some way the gass seems to stick to the biofilm forming in there. And then it gets brown and foaming and slimy and sticking even more..
Looks realy stunning when the fish are swinning in there, for a day, maybe 2 and then you need to clean it Maybe leading a strong powerhead from under it in there to swirl all water around will prevent the build up. And then still you need to suck off the cieling