Filtration is the process that allows us to keep fish alive and healthy outside their natural habitat. It helps clean the water so that the fish can live for extended periods of time without constant aquarium maintenance. Waste products excreted by animals which include ammonia are extremely stressful and life threatening. The primary purpose of filtration is to remove toxic waste products produced by aquarium animals. They work by using a combination of three types of filtration: Mechanical, Chemical and Biological (for a more indepth article on filtration).
EXTERNAL POWER FILTERS
These filters are currently the most widely used due to efficient filtration, simplicity of use, and reasonable cost. They hang on the back rim of the tank, with an uptake tube that extends down into the tank. Water is drawn up the uptake tube where it flows into a chamber where media filters the water. Various designs exist, and they usually manage to perform the three types of filtration (biological, mechanical and chemical) efficiently. The main difference found between the many brands and models is how much water is moved through the unit per hour and the ease of media cleaning and changing. For efficient filtration of an aquarium, turning the tank’s volume (in gallons) over 3 to seven times and hour is preferable. This means that for a twenty gallon tank, a filter that pushes 60 to 140 gallons per hour through it is ideal. As the media clogs with detritus, the optimum flow rate may decline, so it generally good to err toward the higher end of flow rates on a filter.
Canister filters are also external power filters, but generally sit under the aquarium due to their size and weight. They push or pull water through a set of media outside the tank in the filter housing. Canisters are a little different, though, in that they filter the water in a completely sealed, pressurized container. Water is again pulled into the unit through an uptake tube and passes through various media before being expelled to the aquarium again. Canister filters employ powerful pumps to move the water, so the flow rates are often in excess of what might be found in an external hang on power filter.
The main benefit of canister filtration is that the filter itself is virtually invisible, since the bulk of it resides beneath the aquarium, in the stand. Additionally, the powerful water movement and exceptionally large space for filtration media allows these filters to be used on large tanks or small tanks with large bio-loads. With quick disconnecting hoses, it is even easy to perform maintenance by taking the filter to the sink, so there is little mess and no spilled water.
WET / DRY TRICKLE FILTERS
Trickle filters are an evolution of standard filters, trying to be more efficient in less space. The basis on which they were developed is the recognition that aerobic bacteria are the primary focus of all filtration (biological filtration). To maximize populations of bacteria, then, a filter needs to maximize not only surface area, but oxygen as well. Oxygen is much more prevalent in air than it is in the water.
Instead of submerging the biological media under water, it is held in a chamber, as water is dripped or sprayed over it. Due to the high contact of air to the wet media, the bacteria grow in a wet-dry, super saturated oxygenated state. This means there is more “free” oxygen left in the water itself for fish bio process since it is not being used to support bacteria life. Bottom line is that more fish biomass can now be kept in the aquarium. Most trickle filters employ a filter fiber as a pre-filter to do most of the mechanical filtration. Bio-balls, DLS material, bio-stars, and more are the media used for biological filtration.
Despite the advantage of maximal filtration in minimal size, trickle filters do take up some space, requiring that they typically be located underneath the tank, in the stand, like a canister filter. However, because the system is not sealed and under pressure like a canister, a means of transporting the water to and from the filter is needed. Overflows are the choice of getting water to the filter. These consist of a standpipe in the aquarium or a box suspended inside the tank with a strainer and a box outside the tank connected via a hose to the filter. Water then arrives at the filter, called a sump, where it passes through the pre-filter and into the trickle chamber. After this, the water proceeds to a last chamber containing a water pump to push the water back up a hose out of the sump and into the tank.
As previously mentioned, trickle systems can be very useful, especially on large tanks and can be used efficiently on fresh or salt water tanks. They house such incredible numbers of bacteria that once started, will ceaselessly convert all ammonia into nitrate. There are some drawbacks to these systems, however. Size considerations are one factor in deciding if this is the correct system for an aquarium. Many stands will not accommodate appropriately sized filters. The non-sealed aspect of trickle filters can make them prone to overflowing and flooding. It is very important to make sure all the pieces (pumps, overflows, sump size, etc.) work together as a unit. Be sure to perform a “fail – safe” test on the filter system in case of a power failure. When the power shuts off, the tank will drain down to the sump below to a certain level before it stops ---- be sure the sump is large enough to handle this volume of water during the test.
Protein skimmers are perhaps one of the most influential developments in keeping saltwater aquariums. They have made it possible to maintain very high levels of water quality for extended periods of time. Protein skimming may also be known as foam fractionation, and the concept behind it has been in use for decades.
Protein skimmers function in a deceptively simple manner. Foam is created by mixing dense saltwater (doesn’t work with freshwater) and air together – the finer the mix the smaller the bubbles, the more efficient the skimmer will work. Proteins and other organic molecules stick to the bubbles, which creates a stable foam that rises above the mixing air and water. This foam is then collected before it is returned to the tank.
The wastes, organics, and proteins that are collected are pulled out before they have a chance to break down into ammonia. This effectively scrubs the water clean, removing all manner of waste materials from the aquarium and making the biological filter more efficient.
Skimmers do need to be monitored regularly to make sure they are performing well, and not just taking up space and energy. Additionally, because they are so efficient at extracting proteins from the water, they sometimes pull beneficial material like organic molecules that corals use for nutrition and plankton that filter feeders consume. This underscores the need to perform regular water changes, to re-supply the tank with proper nutrients, buffers and salts to make sure all the animals are properly cared for.
Ultraviolet sterilizers work by passing water through a sealed tube with an ultraviolet light; the light emits rays that sterilize or alter the DNA of living organisms that pass by it. Because this is fed by a pump with a pre-filter, large animals (like fish, etc.) are not harmed. Bacteria, protozoan, algae cells and parasites are all killed with this method. The key to using one of these is to size it correctly to the volume of water.
UV sterilizers are generally connected “in line” between the aquarium and the filter system. The UV light bulb is effective for about 6 months and then needs to be replaced.