General Explanation of a Complete Filter System Using a Euro-fil Sump Dave's Recommendation for Saltwater Filtration We emphasize live rock as this is where good bacteria will live and multiply. These bacteria remove toxic ammonia and nitrites. This is categorized as biological filtration. Two other kinds of filtration we'll be pointing out are mechanical filtration where debris is trapped and removed; and chemical filtration where chemical compounds are used to clean the water. +++ 1. Aquarium This is the aquarium where live rock and sand provide biological filtration. As water passes through the live rock, bacteria within the rock break down waste removing toxic ammonia and nitrites. +++ 2. Filter Sock Water moves from the aquarium through the filter sock into the sump. The filter sock traps pieces of dirt and debris. This kind of filter is categorized as a mechanical filter. +++ 3. Sump Water moves from the filter sock into the sump. Place carbon in the sump to keep the water clear. Carbon is categorized as chemical filtration. Also, add live rock here for additional biological filtration. +++ 4. Protein Skimmer moves from the sump into the protein skimmer via a small pump. (Pump not displayed in our picture.) Protein skimmers mix air and saltwater rapidly causing dissolved waste to separate from the water, creating foam which collects in the cup of the protein skimmer. The cup must be emptied regularly. This is also categorized as another form of mechanical filtration. +++ 5. Pump One that there are two pumps pictured in the sump, #5 and #7. We highly recommend two pumps - in case one fails. If you are out of town during a pump failure, one pump will save the lives of your livestock. It's very important to keep water moving. We'll explain pump #5 (as pictured) here. This pump moves water from the sump into the spray bar. +++ 6. Spray Bar The pump moves water from the sump into the spray bar. The spray bar is connected to multiple return lines which move water back into the aquarium. The purpose of the spray bar is to evenly distribute water pressure into the return lines to your aquarium. +++ 7. Pump Two This second pump pictured pushes water through the ultra-violet sterilizer, chiller, and then back into the aquarium. +++ 8. Ultra-Violet Sterilizer sterilizers kill free-floating parasites, such as the ich parasite, dramatically reducing the spread of disease in the aquarium. They also help to control the growth of nuisance algae. You may use a separate pump, or connect the UV in-line with one of your return lines to create water flow through the UV. Water enters the UV sterilizer and passes by an ultraviolet light that kills the free-floating parasites. +++ 9. Chiller  A chiller may be needed to keep the water temperature constant. (You may also consider a heater, which is inexpensive and may be placed in the sump.) +++ 10. Aquarium Water moves back into the aquarium. NEXT: Plumbing Parts Explained