Rockm is right...without air movement fungus will be a problem. Check out what I built
here. I designed the dresser greenhouse with a fan to circulate air and prevent fungus growth. It has worked well. I placed a plastic baffel up inside the top plate so that air would not be directly blowing on the plants. The fan was a squirrel-cage type from a Big Box Store and it is fairly quiet.
Maybe you could build a smaller desktop model of my dresser greenhouse or find a way to add a small fan to the top of your aquarium.
Not many comments on my original Dresser Greenhouse thread probably because most people think it is too big for their house, too much $ or too much trouble for the end result. However, it is working really well and was gratifying to build.