it isnt necessary, but you may just want to change you water often, because it will become dingy and dirty. filters just help, but not necessary. you can just use smaller powerheads to move water from one location to the next, and a sump would be one way of doing it. another would be to creat a false bottom and sticka power head under there with a hose leading to a type of water fall. any local fish store will have small powerheads. theyre used for current in fish tanks, and can certainly be used for "moving" water within your tank.