A water purification system creates an integrated, small-scale marine or fresh water ecosystem that is particularly useful as a home, school, office, or laboratory aquarium. In operation, water from the aquarium tank is routed to an algal turf scrubber screen or equivalent algal-growing surface placed in a movable, tray-shaped receptacle. An algal turf, comprising preferably a dense colony of microalgae, resides on the screen. As the receptacle fills with water, the center of gravity of the receptacle moves across the axis of the pivots upon which the receptacle is mounted. At this time, the substantially filled receptacle rotates on its pivots and the desired surge effect across the scrubber by the exiting water is achieved. The surge, light energy provided by lights above the receptacle, and algal photosynthesis promote metabolic cellular-ambient water exchange to remove carbon dioxide, dissolved nutrients and organic compounds, and other pollutants. Oxygen is also released into the water. The substantially emptied receptacle returns to its horizontal position and the purified and oxygenated water is then returned to the tank. A linear or rotary vibrating motor may also periodically cause water to surge across the screen. In addition, other appropriate components of the ecosystems may be included, such as tide creators, high intensity, broad spectrum artificial lights over the tank, salinity controllers, pH controllers, sediment removers, temperature controllers, automatic feeders, timers, and the like.