The sand filters are similar to what you would find in a home swimming pool, but on a much larger scale. The pumps force water through the sand at 15 to 20 psi, and the sand traps debris. The system can automatically backwash sluggish filters, and the staff changes the sand periodically.
In a protein skimmer, water from the exhibits passes through the filter, which injects air at a very high velocity. A venturi valve -- a tube with a constricted area in the center -- breaks the air into micro-bubbles. These bubbles have a lot of surface area for debris to cling to. The foam that this process creates overflows from an opening at the top of the filter and falls into a collection chamber, which the staff must clean periodically. Check out this Marine Depot article for more detail about protein skimming and venturi valves.
This process naturally requires a lot of pumping, which can produce dissolved gasses that are harmful for fish. So, the system pumps water up into holding tanks above the exhibits and allows the dissolved gasses to dissipate. Then, gravity pulls the water back into the habitats. Heating or cooling a small amount of water before return to the exhibits helps keep them at the correct temperature.
This system sounds complex, but a computer handles nearly all of the decisions regarding clean and dirty water. Eleven computers connected throughout the building make 150 million decisions per second involving tank levels, temperatures and pumping flow, all of which are critical to animal health and system operation. The computer uses graphics and data to provide information and feedback to the life support staff.
Even though the system is almost 100 percent self-sustaining, the staff still takes samples from every exhibit every day, analyzes them in a lab, and adds any necessary chemicals by hand. Water chemists evaluate the nitrogen cycle -- the breakdown of organic material into nitrogenous wastes -- as well as ammonia levels, pH, salinity and oxygen in water samples from every habitat every day. An ion photography system measures, dilutes and analyzes samples, recording anything that is positively or negatively charged. The staff also uses a high performance liquid chromatography system for research-based applications.
Research is important to the aquarium's mission and to its status as a nonprofit organization. We'll explore other research and education programs in the next section.