You dont want plants that are to big if there plastic, or grow to big if there live. I would get about 2-3 medium sized plants for the back, and about 3-4 small plants for the front. Then you can add a rock, or the corys would love a small clay flowerpot on the bottom. All you need to do for that is get a small clay flowerpot, and take a hammer and screwdriver. Then put the screwdriver on the bottom of the pot, and carefully hit the screwdriver with the hammer, until the base is gone. I would recommend doing this over newspaper, and wearing goggles. Don't forget to wash the items before putting them in.