Biological Filtration

• Biological filtration is the use of bacteria and other organisms, and to a lesser extent plants, to convert your fish's toxic waste into less toxic substances. Your fish digest food and excrete feces and urine into the water. Your biological filter converts toxic ammonia into nitrite which is then turned into nitrate. This process is called cycling, and it occurs as the water passes over any surface that the nitrate can grow on. All aquariums need to have a biological filtration system to keep fish healthy, but you still need to remove the nitrate by water changes or an additional filtering method.
  
  

Chemical Filtration

• Chemical filtration works by aggressively using carbon or chemical resins to remove toxins from your tank's water. The carbon works until it becomes saturated. It is important to regularly remove activated carbon from your tank. It is important to change saturated chemical filtration or else the filtration system will begin to release the toxins back into the water.
  
  

Mechanical Filtration

• Mechanical filtration works by separating undissolved waste particles from the water. It cannot filter dissolved wastes in the water. Most systems use a sponge, floss, filter pads or dense bubbles to remove large particles such as decayed plant matter, dirt, waste particles or uneaten food. The tank's water is pushed through the strainer and the large particles are not small enough to go through. This method of filtration is not recommended for saltwater tanks.
  
  

Protein Skimmer

• Protein skimmers work by using condensed air bubbles to push the toxins up a cylindrical pipe to the surface of the tank. Protein skimmers are clear plastic tubes that use a water pump to push the water into the cylinder. Inside the cylinder, condensed bubbles bring the toxins and proteins to the surface. The foamy scum that is on the surface of the cylinder is then pushed into an enclosed compartment, a collection cup. It is recommended to use a large protein skimmer for optimal cleaning. Protein skimmers are an especially good method for saltwater reef tanks.
  
  

Warning

• Most tanks need multiple filters. Saltwater fish are sensitive, and multiple filters will keep your tank at its cleanest. If one filtration system is not doing its job then there is another to fall back on. Even with a good filtration system make sure you are regularly changing the water in your tank. Also be aware that over-feeding your fish, or keeping too many fish in too small a tank, will make it harder to keep the water clean.