Equipment you more than likely need:
There are many different types of filters. Which filter is best really depends on your setup.
The water in your tank should be filtered 4-6 times per hour. There are three different kinds of filtering: Chemical, Biological, and Physical.
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# Physical filtration - use of physical filter media
# Chemical filtration - removal of chemical contaminants
# Biological filtration - natural bacterial decomposition of waste
Physical filtration is the process of physically removing particles of debris and waste from your aquarium. This level of filtration should be the first line of defense. Normally this is accomplished by passing your tank water through some sort of porous media to catch the particles like a strainer. Some of the most common types of physical filter medias are floss (waddings of polyester or similar cottony material), course and/or fine strainer cartridges, and filter foams. The finer the texture of the filter media is, the smaller the particles it will catch but also the faster it can get clogged and need to be cleaned. Some physical filter media can grow beneficial aerobic bacteria and become a partial biological filter.
Chemical filtration is the process of removing contaminant chemicals from aquarium water by means of chemical absorption. This level of filtration should be the second line of defense. Many hang-on back filters have pre-assembled cartridges for purchase which contain a small quantity of charcoal (carbon), which absorbs many harmful chemicals from your fish tank water. Another commonly used chemical filter is zeolite, which is known for its ability to absorb harmful ammonia. Many aquarists choose to mix charcoal and zeolite together in their chemical filters to remove a wide variety of contaminants including harmful metals, ammonia, chlorine, household toxins, etc. An aquarium filter is most efficient when used AFTER a prefilter or physical filter so that debris will not build up and clog the absorption capability of carbon and zeolite.
Biological Filtration is the process of passing aquarium water over a media which is designed to grow aerobic bacteria, beneficial to the breakdown of harmful ammonia and nitrites. Biological filter media is usually course, and includes sponges, foams, course ceramic or porcelain pieces, or any porous material that has sufficient surface area to grow bacteria.
A combination of all 3 of these filtration media types is the most efficient way to properly filter your aquarium water.
Just to list a few types.
Canisters are an external filter which is usually placed below your aquarium within the stand, and is used primarily for physical and chemical filtration but can also hold biological media for. A canister filter works like this - an electromagnet pump powers a magnetic impellor, turning it very rapidly when this unit is powered up. Aquarium water is drawn into the intake tube and travels down the plumbing and into the filter, where it then passes through all of the filtration media. The pressure inside then forces the cleaned water back out through a second exhaust hose, and back up into the aquarium. Some canister filters are small enough to hang on the backside of your aquarium, similar to the hang-on back filter. The difference between the two is that the canister is a water-tight sealed filter. There are many sizes and types of canister filters, but it is always best to follow the Golden Rule of fish tank filtration - filter your water 5 times every hour. It is very important that an aquarium canister filter always has a tight, straight and clean water-tight seal. If air bubbles get into the impellor, then proper suction of fish tank water through this device is significantly lost or lost altogether. Re-seal your filter properly, making sure the seal is very clean and that the rubber gaskets are fresh, uncracked, and untwisted. The use of a thin coat of Vasoline can assist with making sure the seal stays water-tight.
Hang on the back filters
Hang on the back filters are one of the most common in the aquarium arsenal to keep fish tank water clean. This filter type literally hangs on the backside of your aquarium, drawing water up through an intake tube and into the body of the filter through various filtration media including charcoals, zeolite, and physical mesh filters. These filters are powered by an electromagnetic pump which, when plugged in, spins a small impellor that creates the draw of water through the intake tube. Water then passes through filter cartridges and sometimes over a biological filter media or "bio-wheel", and then overflows over the return spout and back into the aquarium.
In a heavily populated aquarium, saltwater aquarium, reef tang, or living plant tank, this filter will not be very beneficial. It is a slightly less efficient filter than the above mentioned types, but it is very affordable and effective for filtering the average home aquarium with freshwater fish and animals. An undergravel filter works like this - a hollow plate with holes/slats is placed at the bottom of the tank below about 1 1/2" to 2" of medium/small gauge gravel, and water is drawn through riser tubes through the gravel and out these tubes back into the tank. There are a couple ways to power this filter. The most elementary way to power it is with rising air bubbles in the riser tubes. Air is pumped through tubing into the bottom of the riser tube (never under the plate!), and the rising bubbles slowly draw water up with them. The water is slowly drawn through the gravel on the hollow filter plate, and your gravel acts as the physical and biological filter media. Another way to power this filter is with the use of a powerhead pump. This pump is a small electromagnet motor which spins a magnetic impellor inside the pump, drawing water very strongly through the riser tubes and back out over the gravel. Powerhead pumps are truly the best way to run your undergravel filter efficiently and get the flow rate that the tank needs. Remember, use a powerhead combination that will be able to cycle your tank water 5 full times per hour through the undergravel filter. IMPORTANT: make sure to regularly clean the gravel in your tropical fish tank on a regular basis, usually weekly, to maintain the health of your tank with the use of this filter. 5 minutes a week is all it takes to sufficiently vacuum the gravel in your aquarium and keep your fish tank crystal clean.
Sump, Trickle, and Wet/Dry Filters
The largest filter of them all is the sump filter, or also called the trickle filter or wet/dry filter. The name "wet/dry" derives from the fact that this filter has a "dry" chamber of biological media in the upper tower, and a "wet" section called the sump. The biological media isn't truly dry, but is not fully submerged and only has water trickling down over it. This filter consists of a large water-tight box with an upper chamber of porous biological filter media, a barrier of prefilter foam, and sometimes the use of a carbon/zeolite chemical filter media. The fill rate of a wet/dry filter is controlled by gravity through the intake tube. Since this filter is kept below the aquarium, gravity's pull on the water in the intake tube acts like a siphon and draws water down into the tower box. Water trickles usually first through a large sponge prefilter which can be easily rinsed as large debris builds on it. Water drains through this spongy material and disperses onto the "trickle tray" - a flat tray with many small holes drilled in it which makes the aquarium water evenly "trickle" or rain down over a large box of biological filtration media. As the water trickles over this porous material which is rich in aerobic bacteria, the bacteria breaks down the ammonias and nitrites in the water. Finally, as the water filters through into the bottom of the sump box, the water is passed through carbon and/or zeolite either through cartridges or mesh bags, and is then pumped out of the bottom/side of the sump box with a large pump and back into the aquarium through flexible tubing or plastic plumbing. This filter type is most commonly used on very large systems, complex and overloaded aquariums, and large saltwater/reef setups. The trickle effect of the water over the bio media keeps the bacteria thriving and highly oxygenates the aquarium water before it returns to the aquarium.
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