There are many methods that can be used to achieve the goal of a beautiful reef aquarium. One aspect of aquarium care that is often intensely debated among reef keepers, and can be confusing to new hobbyists, is filtration. There are several commonly used filtration methods for reef aquariums and I will discuss some and present the benefits and drawbacks of each. Each method can be quite detailed and complex so I’ll cover them basically on our Reef Equipment page to give you an overview.
Most filtration methods are based on biological processes. Waste and left-over food in your tank are utilized by bacteria that breakdown the material into various components. Bacteria are present in vast numbers when we add live rock and live sand to the tank and this serves as the basis for the system’s filtration.
THE CORE OF MOST
Bacteria will breakdown the waste and attack leftover food and can eventually convert the toxic wastes into less toxic byproducts. Initially ammonia is produced and bacteria will convert this toxic waste material into nitrite, also quite toxic to most marine animals. Bacteria will convert this toxic nitrite into less toxic nitrate. The bacteria that have converted the ammonia into nitrate do so in an environment with oxygen, they are aerobic bacteria. In an environment without oxygen anaerobic bacteria will breakdown the nitrate into nitrogen gas that can safely be emitted from the system.
The basic process of waste processing is called the nitrogen cycle and is what occurs in our aquariums. Other biological processes are ongoing too and create a complex web of constant changes in your tank’ s environment that all impact water quality and filtration. The goal of any filtration method is to create a cleaner environment for your tank’s inhabitants, use of bacteria is usually at the core of this.
Aerobic bacteria that grow in the presence of oxygen are always present in our aquariums and these are certainly needed for waste processing. However, if only aerobic processes take place which convert ammonia to nitrite and then nitrite to nitrate in time the concentration of nitrate in the aquarium will increase to undesirable levels. Reduction of nitrates is accomplished through water changes to dilute or via the utilization of anaerobic bacteria that utilize the nitrates and convert it to nitrogen gas.
Nitrates can be kept to a minimum by having a bare bottom tank with lots of flow and a large skimmer to remove waste before it has to be broken down via the nitrogen cycle.
One of the oldest methods of purifying your tank’s water is simply exchanging it with new water. This process of literally removing water from your tank and exchanging it with new water is called a partial water change. A partial water change not only dilutes pollutants in the remaining tank water but it also replenishes depleted chemicals and other substances needed for your tank’s inhabitants. Theoretically you could keep a tank superbly clean by constantly changing some water. However, this can become costly and disturb the tank’s inhabitants if you were not careful to put back water at the exact same temperature, salinity, pH, and other parameters. Remember that we are trying to reproduce conditions in our reef aquarium as they are on the natural reef, which tend to be relatively constant. Continual water changes are not practical in the long run for most hobbyists as the sole method of purifying their tank’ s water. Small periodic partial water changes are beneficial, and should be performed approximately at the rate of 10% per week regardless of the filtration method employed.