What Fish Tank Filters to Buy

So I’ve been looking into what type of fish tank filters I need for my freshwater fish tank and there are many variables to consider.
Fish tank filters with large and fast throughput are not necessary in a small aquarium and even not necessary in a large aquarium containing a small number of calm-water fish.
On the other hand large messy fish do require a large and turbulent filter to clean up their detritus and a large volume of bacteria to process it.
On the other, other hand a low throughput filter is adequate for a large tank with many small fish in it.

I’m confused?

External Canister Fish Tank Filters

Usually a plastic container with pump located below the aquarium.

These filters can be any combination of mechanical, biological and chemical depending on the filter media I put in the container.
The water is siphoned into the container because its below the water level in the aquarium, passes through the filter media and is pumped back into the tank.

Internal Canister Fish Tank Filter

A submersible pump is located on top of the filter media container and all is submerged in the aquarium.
Water is drawn in through slits in the side of the container, passes through the filter media and exits via the pump at the top.

Hang-on Power Fish Tank Filters

Consist of a plastic box containing the filter media hung on the outside of the aquarium.
Water is drawn into the filter via an intake tube hung over the edged of the aquarium. The water passes through the filter media and returns to the aquarium via a channel integrated into the bracket holding the box to the side of the aquarium.

Under Gravel Fish Tank Filter

A very effective biological filter with a large volume of media, the aquarium gravel or sand bed.
A large plastic plate full of holes is laid on the bottom of the aquarium and covered in 5 cm of gravel or coarse sand. Uplift tubes are fitted to the plate. An air-pump pumps air into the bottom of the uplift tubes and by the airlift principle water is drawn through the gravel/coarse sand and up through the uplift tubes and back into the aquarium.
As the water from the aquarium is drawn down to the plate it brings with it the solid and liquid waste in the water into the gravel/sand bed where the friendly bacteria eats it.

Water Changes

One last note.

Biological filters take care of the ammonia and the nitrite produced in the aquarium but over time the concentration of nitrate increases.
Aquarium plants can take care of some of this nitrate but not all.
So, regular changes of water is necessary. Not all the water. Only 10 – 20% at one time.
And if I’m leaving the fish in the aquarium while I’m doing this, I need to take care and make sure the new water has the same chemistry and temperature as the existing. Or, my fish will suffer.

Swordfish