What types of fish tank filters are there you ask? Quite a few, some are better than others!

So you need to figure out what fish tank filters are out there and which you should choose right?

I knowwwww... when you look them up there is just a dazzling array of them right? Some big, some small, some cheaper than others. How do you figure this stuff out??

Well firstly there are quite a few kinds and it really depends on how much money you want to splurge. Lets look at the simpler ones first and then get to the nice and cool ones.

Internal Filters

The simple and cheap fish tank filters are the kinds that are 'internal' to the fish tank i.e. its something that you put inside the aquarium water with the fish themselves.

Corner internal filters from a generic brand, corner internal filters are a nice choice for internals, sits tidy in the corner and works decently.

Bottom internal filters are really bare bone in terms of internals. You would want to get a corner filter as well if you choose these.

Usually they will need a connection to a fish tank pump whereby the air being pushed through the filter will help water to flow through and therefore any visible fish crap will be caught up by whatever filter media you might have in the filter itself.

These aquarium filters tend to be small so at most you can put only some white cotton fiber material and maybe some sand and stones as the filter media.

This is a really tiny internal filter

Case in point, its basically half motor on the right with the little fan, and half a case for small filter media on the left.

A close up of the fan and notice the 2 suction cups to hold the filter in place

Just enough filter media, smaller than the palm of your hand! (did I say this was a tiny example? or did I say tiny? :) ) Also notice the suction cup on the left.

There is also the 'undergravel' type of aquarium filters, which essentially has the same concept above but instead of being a box of some sort which holds filter media, this filter literally covers the floor of the aquarium and the same principle of passing air bubbles through hold as well.

There are also more expensive internal filters which may house more filter media and have more ability to move more volumes of water through it than the cheaper ones and therefore, at least in theory, 'clean more water'.

The coolest internal filter I have seen and likely one of the more effective ones as well.

Its not just cool but also brilliantly sectioned to allow for different types of filter media.

You can see inside that several sections are available. Were you wondering now why you saw circular filter media somewhere?

The fan used for this internal filter is firstly built in so there is no need for a separate air pump but secondly, come on, its cool isnt it !?

Internal fish tank filters are decent, do the job fine for small to medium fish tanks. They are by no means ideal, however. They are okay for a few small fish and would be a good start for newbies.

External Filters

The second group of fish tank filters are basically external to the fish tank. In such cases, water is basically taken out of the fish tank and flows into a filtration system and the filtered water is then flowed back into the aquarium.

These have a couple of styles as well.

The first of these external aquarium filters, which is the least effective among the lot (but still, in general more effective than internal aquarium filters) are the ones that have a pump in the fish tank that sucks water out of it and passes the water into a filter that resides above or to the side of the fish tank itself.

Then by gravity, the water will drop back down into the aquarium via an excess water pipe, after it has passed over a series of filter media.

So why is this the least effective?

Well it has the drawback of allowing excess, unfiltered muck and other bad stuff to fall back into the aquarium.

This will tend to happen especially when the filter media is already saturated or the filter media is not placed in a way that is optimal to catch the dropping water being sent up by the fish tank pump.

However, with diligent, well understood water quality and predictable scheduling of filter media cleaning, this filter method is decent. Its also the cheapest method among external aquarium filters.

There are also varieties where the water drops back in to the aquarium like a waterfall and so can be quite aesthetically pleasing.

Unfortunately these types tend to be small and therefore have little space for filter media and so depending on your fish tank size, number of fish and how big they are, these may not be too effective.

Still, they look pretty cool! And yeah they are okay for a few fish.

an obviously 'used' waterfall external filter but hey at least it gives you an idea of what it looks like!

Take note of the 2 filter media 'boxes' on the left. When the water is sucked in, it is sent to the left compartment 'passing through' the filter boxes and exits above as a 'waterfall'.

The second external fish tank filter type also uses fish tank pumps. However, instead of pushing water up into a filter setup, it actually pushes water up into the fish tank from a filter enclosure below the aquarium.

Basically, the aquarium itself will then have an 'excess water' exit or hole whereby water will then drop back into the filter enclosure below and gets filtered from passing through the series of filter media.

The series of filter media will also tend to be in different compartments so as to further encourage visible and invisible waste to settle or be consumed by good bacteria. The filtered water will flow towards the fish tank pump and will get pumped back into the fish tank and so the cycle continues in this way.

Hence, the filter media in this case is below the fish tank rather than above or to the side, as in the first type.

These sorts of fish tank filters tend to come 'custom made' with certain types of fish tanks. Usually the larger ones. Hence, its price is embedded in the cost of the fish tank itself but its well worth the investment.

As you can probably tell by now, its first major advantage is that nothing 'falls back' into the aquarium since everything has fallen beneath the fish tank into a separate filter enclosure.

Also, last I checked, gravity will not pull anything upwards! :)

Immediately, you have the advantage of getting less fish muck and other bad stuff going back into the aquarium via gravity. Of course, if you dont change your filter media often enough, some of the muck will escape and get pushed up by the fish tank pump back into the aquarium.

A more expensive external fish tank filter essentially has the pump and the filter enclosure built together in one setup. They will tend to have one pipe that shoots water out, and another pipe that sucks water in.

This filter setup (and they tend to look like miniature R2-D2s, I kid you not!) will have a series of filter media built within it. It has the same advantage as the one described above.

R2-D2 like External Filter, how do you beat that Obi-wan? :P

Another view of this great external filter

One tube takes water in, and another one sends it back out

The lock mechanism that keeps the filter air tight

An inside view of the filter

The first filter layer...

Followed by the second which is a really a double layer. Black filter media with rings below.

The brains of the operation, moves the water in and out.

There are those who will argue these are better and some others, that the customized built in ones are better. I dont have a particular preference, they are both external fish tank filters and should work better than internal fish tank filters. (Unless you are a Star Wars fan, in which case you will feel the force and know your preference!)

The real difference is cost and how disciplined you are at checking the filter media :). Generally, the larger the fish tank filter (the customized ones tend to be quite large), the less often you need to check on the filter media.

So there you go, a thesis on some of the common fish tank filters. Phew!

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