So I am in college, and want to start up a small aquarium to keep in my dorm. We have a 20gal limit for dorm policy, and my funds are also limited. I have a betta in a small bowl with rocks, a fake plant, and a little castle. He is content, but it is so boring. My mother is going to give me her old 10 gallon tank from her old freshwater setup, which includes a filter, heater, light, etc. I'm a newb and don't know too much about fish and what I can keep. From doing some online research, I heard its better to do freshwater than saltwater. i just want something interesting to watch with alot of movement, colors, and life. I want it to look natural kind of like a lake bottom or something. Any ideas what to do?