Modular terrarium

Stackable terrariums which, when assembled, have a single landscaping theme, for snakes, lizards, and insects that would try to decimate one another if not separated.
The way he explained it to me there would be boulders with small cactus and shrubs around the base of some gnarly tree, but each terrarium would have only a single piece of the landscape per cube.
Secondary application:
He thinks that a way to farm spider silk may be achieved this way by culling the spiders that continually try to attack the others through the glass. After several generations he thinks that co-existing spiders may be bred.