As for tank size, search garage sales and thrift stores for aquariums, the bigger the better (20L minimum) and you can order a good metal mesh screen from Amazon. The larger size isn't a problem, wild corns are born into a whole world in which to explore, not just a couple of square feet, but they do like their hides a lot, and if you "clutter" the bottom with plastic and silk vines and aquarium plants they will be happy and you won't have to shell out more money when the time comes.