Aquarium Filters are needed to keep your fish tank clean.

There are many types of fish tank filters that can be used based off of your needs.

Canister filters such as the JBJ EFU lines offer multiple benefits compared to a commercial HOB or hang on back filter.
Canister filters will be under your tank typically in a stand or on the floor.  The filter media provides a few types of filtration to keep the water clean.

These methods are chemical, biological  and mechanical.  The JBJ EFU canister filters offer UV light as well which is a bonus as it sterilizes the water essentially zapping the bugs and disease the passes through it with UV (Ultra Violet) light which helps destroy diseases,

We sell protein skimmers for the Nano Cube as well which remove accumulation of excess gunk and protein from saltwater fish tanks only.  This does nothing for a freshwater aquarium.

The MSS surface skimmer however can be used on both tanks and acts as a prefilter and also helps make sure small fish do not get sucked in your overflow filters.  These were first seen on the Nano Cubes.