You could suction cup it to the glass walls, or drill a hole through a rock or a log and stick it in there as a base (although good luck witha rock you'd need a strong drill bit) or silicon adhesive it to the walls and floor just let it air out for a day or two before adding the corns. Or you could tie a few sticks together to make a free standing structure like a tower or something that supports itself (like a teepee without the buffalo hide)
Missy