A filter is not necessary but it certainly takes the hard work out of fish keeping.  If you have a small fish bowl or fighter tank then you won’t be able to set up a filter, and you’ll need to empty and clean the tank regularly.

If you have an actual fish tank, then you can buy a filter to fit the size of your tank.  Most filters will have a guide on the side telling you what size tank they are designed for.


There are two main options when it comes to filtration.  It’s easiest to separate them into above gravel and below gravel (or under gravel) filtration.

Picture from

This is an undergravel filtration system.  As you can see the “dirt” (keeping it clean here) sits on the top of the gravel, breaks down and then gradually works its way down in to the gravel all the way to the bottom.  If you have an under gravel filtration system the dirt passes through the gravel and to the bottom of the tank past the plastic under gravel sheets, to sit on the glass bottom of the tank..  Here it is sucked out by the filter, up and out.

Where as an above ground filter does the following:

Photo from

You can see that this filtration system does not interact with the gravel at all.  The down side is that this is only cleaning the water (which is important) but not the gravel.  If you use this filter system you will need to clean your tank more regularly and invest in a gravel cleaner. See Cleaning your aquarium.

Want to buy one? – start by looking here.

I personally much prefer under gravel filtration.

Setting up an under gravel filtration system

To set up an under gravel filtration system you will need to buy the plastic sheets which sit at the bottom of your tank and a filter especially designed for it.  If you have a tank like I do with an above gravel filter built into the lid, don’t fear you can still set up an under gravel filter.  You will need to buy the plastic sheets plus some plastic tubing from your hardware store to connect the bottom of the filter intake to the plastic sheets.  It’s not perfect but if you decorate around it with some rocks or plants no one will know!

The plastic sheets come in a range of shapes and sizes.  You want to aim for one that covers the majority of the tank but not all of it otherwise the system will be visible from the sides.


You will need to empty your tank completely of all fish and decorations.  If you have a two sheet system (as opposed to just one) then you will be able to fit it without removing the water and gravel.  Otherwise if you have just one sheet and a smaller tank you will need to remove the gravel.  Don’t worry it’s worth it!

Push all the gravel to one side and put your first sheet in.  You need to make sure that there is no gravel under the sheets.  This is because you want the dirt to pass through and have no resistance in being sucked out.  Gravel under the sheets would only help the dirt lodge and hide instead of being cleaned out.  Then repeat with the other sheet.

Once both sheets are under the gravel, connect the water intake to the hole in the plastic sheet.  This where you will need the plastic tube to connect them if you have an above gravel filter you are makeshifting into a below gravel filter.

When it’s connected just turn it on full time like you would with any other filter system and enjoy the superior clean!

What to buy one?? – start by looking here


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