How do I choose between internal and external filters?

Deciding between an internal and an external aquarium filter depends on the type of requirements your aquascape has. Internal filters, which mount inside the tank to free up space around your aquarium setup, and external filters sit outside the tank where they can filter more effectively.

Tank size is also an important factor in determining your best filter option. Internal filters are better suited to nano tanks under 10 gallons. They will fit snugly into small spaces and are much less conspicuous. External canister filters can easily process larger aquariums and provide the adequate flow rate that internals struggle to maintain in aquariums over 40 gallons.

If you regularly clean your filter, consider the ease of maintenance when making your choice. Internal filters require cleaning by reaching into the tank, which can disturb fish and plants. External filters with quick-disconnect valves allow you to get them without disturbing your tank.

Noise levels vary widely across types of filters. Internal filters produce very little noise from vibration, so they would be best for a bedroom or office aquarium. External canisters generate a slight increase in operational noise from the motor. If you place an external canister in a cabinet, it will work to suppress the noise from that transmission.

Evaluate the biological filtration capacity of the equipment very carefully. Internal filters don't hold as much biomedia as external filters, and the greatest advantage of external filters is the considerably larger volume within a canister, which encourages colonies of larger bacteria. Internals are that much more effective when bacteria have more surface on which to feed, so try to add some ceramic rings into the chamber if possible.

The budget has a significant influence on your options. Internal filters are lower at the buy-in and consume less power. External filters have a higher initial cost, with a lower price for media. Consider all costs and think about how you will operate the filter in the long term before making a decision.

In unique circumstances, special solutions involve approaches. Breeding tanks must be equipped with internal sponge filters to ensure fry don't escape. Grow-out planted tanks generally work best with external filters that feature CO2 injection ports. Reef tanks often utilize an external filter and a protein skimmer, which are often integrated into a single unit.

Hybrid systems. The flexibility of a hybrid approach may be chosen either to combine internal and external filtration for more challenging setups or make use of an internal filter for mechanical pre-filtration, adding an external canister to accommodate biological and chemical stages (the system combines the advantages of both approaches)

Read the full article: Understanding Aquarium Filtration Systems