Internal Filter v External Filter

Internal Filter versus External Filter:

Selecting a filter for a tank is very important. People usually don’t care & choose any type of filter, & often performance of filter is reduced based on multiple parameters, such as: tank size, planted or non-planted, size & type of inhabitants, decorations, gravels & more. We prefer using a large tank with small fish that do not produce much waste, & keeping less fish can reduce waste, & use a planted, bare bottom aquarium with few decorations so that tank can be properly cleaned using filter. Some filter allows you to adjust water flow speed, while others can be operated using air pump that adds oxygen to tank. Make sure your filter disturbs water so that enough oxygen is added. 

To make things easier, filters are divided into 2 types: internal & external.

Internal filters:

Internal filters are very common because they are powered by a water pump & have a box which contains a sponge. Internal filter sits within the fish tank. The water is sucked in & it passes through the sponge which removes debris & also the sponge holds good bacteria which helps in biological filtration. 

Such filters can be operated using air pump or they are power filters. Famous internal filter is sponge filter, & canister filter. Sponge filters have been used since ages but still people choose to prefer them but they dislike the sponges which affect the appearance of fancy tanks. Canister filters can provide better performance & they are able to provide mechanical, chemical & biological filtration. Canister filters that are located inside aquarium can used sponges for both mechanical & biological filtrations, but modern canister filters contain another sponge for housing higher levels of good bacteria, & one of the sponge can be replaced at a time without losing all of your good bacteria. They can offer adjustable water flow & hobbyists can change direction of nozzle which sprays water.

External Filters:

External filter is installed outside fish tank. Water is sucked out of the aquarium, where debris is removed & then it is pumped back to aquarium. External filters hold more media than internal filters, so they do not require high maintenance.

Such filters use power for operation & they can provide all types of filtration such as mechanical, chemical & biological filtration. Most importantly a healthy aquarium needs a better biological filtration because this is the main reason behind death of large number of fish in aquariums. External filters allow hobbyists to adjust water flow rate, aerate tank, & they suck water from aquarium using a hose. Then water passes through mechanical filtration which removes debris, & allow clean water to enter biological filtration which helps in creating good bacteria by breaking down ammonia into less toxic components that can be removed with regular water changes. Clean water flows back to tank via a hose. External filters may be costly but work like a charm.

Pros & Cons of Internal Filter:

Internal filters are smaller & best for smaller aquariums. The running cost of internal filter is low. Also they are inexpensive. They can remove dirt very well & sponge filters are very helpful in fry tank because fry can eat leftover food attached to sponge. Internal filters produce lots of clutter in the aquarium. Sometimes you will have to replace the whole media, causing a new cycle. Internal filters can be slightly fiddly when maintaining.

Pros and Cons of External Filter:

External filters require low maintenance because they are located outside aquarium & also they contain more media which do not require that much cleaning. There is a large variety of media available in external filters. Filters take up space & do not look beautiful in aquarium so external filters are located outside aquarium. External filters are more expensive than internal filters because they are more sophisticated. External filters are usually big. Media / sponges of external filters are expensive.