Without a proper filtration system, you will never have a perfect, healthy fish tank. Your filtration system will ensure that the water remains clean and clear and your fish will not be poisoned by their own wastes or bacterial overgrowth. However, which type of filtration is best for your tank?
There is great debate surrounding this topic. Each type of filtration system will have its own benefits and drawbacks. Many people prefer a system that is placed in the tank. They are placed in the back of the tank with their outlets located just below the surface of the water. The mechanical system will then suck the water upand let it pass through a variety of materials designed to trap the dirt in the water. There is also a sponge placed in the system that contains several strains of healthy bacteria that remove 
ammonia from the water. After the water has been cleared it will be released back into the water.
Outer filtration systems, on the other hand, are usually placed outside of the tank in the cabinet below it. It functions quite similarly to a cleaning system located on the inside of a tank. However, these types of systems contain more cleaning materials than other types of systems. This means that it requires less frequent cleanings than other systems. The real difference between these two types of cleaning systems becomes clear when you look at the price. An outer filtration system is often a lot more expensive than one that can be placed inside of your fish tank. The type of filtration system you decide on depends largely on the needs of your fish tank. If you do not have the time to perform regular maintenance you may want to consider the outer version.