They're nice to put on top of a desk or coffee table.

What it sounds to me is that you need to be much more sterile in your work. If you're growing on cakes (what kind of substrate are you using?) If you've got a substrate made or brown rice flour/verm and water...and if you do everything somewhat well, you might end up with cobweb mold. But if you end up getting green,blue, and other color contaminate....thats a sign that the work and growing conditions weren't very clean.

I'm not sure what exactly you did but just remember that the cleaner you are while growing the happier your little buddies will be;-)