Aquarium filters are an essential piece of kit for any fish tank as they work to remove all the waste produced by the fish as well as any debris from plants and food waste too. Without a filter, this waste will build up and pollute the water, which can kill the fish.
However, there are many different types and sizes of filter so choosing the right one for your particular tank can become a challenge with an overwhelming number of options. Choosing the best filter for your aquarium is vital for the health of your fish so here are a few things to consider:
- Mechanical or biological filter?
There are two different types of filter to think about – mechanical and biological. The mechanical kind work by physically trapping the waste and removing it from the water, so you can empty it out later.
The biological kind use bacteria to convert the harmful waste into less harmful substances which you can then remove when you change the water in the tank.
It’s important to know both types take time to start working so you need to get your filters installed well before you add fish to your tank.
- Internal filters
The most commonly used filters are internal power filters – they have a small water pump within them and sit inside the aquarium. They work by using a sponge which traps the debris and the bacteria within the sponge will convert any nasty waste into nitrates.
You will need to rinse the sponge every few weeks to remove any trapped debris but make sure you don’t rinse it under the tap or you will kill all the bacteria inside it. Just syphon off some of the tank water and use that.
- Under gravel filters
Another type of filter option is an undergravel filter – you often see these in older or budget fish tanks as they are considered somewhat old fashioned now. The tank comes with a tray, which creates a false floor in the aquarium.
This allows a layer of gravel to sit above a space filled with water. A pump is attached which creates suction, pulling the water and any solid waste into the gravel. It traps the debris and the oxygen provided by the suction mechanism encourages bacteria which then convert the debris into non-harmful substances. They can take a lot more work to maintain but are cheaper to buy and run.
- External filters
If you have a large, sophisticated set up you might require an external power filter which sits outside the tank. These work by sucking the water out of the tank, through the filter which cleans it and then pumps it back into the tank.
These filters don’t need as much manual cleaning as they have more media inside and they can be quite versatile. If you have a large tank or fish which produce a lot of waste, this is probably your best choice, although they can be the more expensive option.
- What sizes do filters come in?
When you are looking for a filter, check the packaging as it should tell you what size of tank it can cope with and you need to make sure the filter is big enough for the size of your tank. The packaging should tell you what aquarium size the filter is capable of supporting. Look for a filter that is capable of running a tank at least as large as yours, ideally a bit bigger.
- Do all filters use carbon pads?
Carbon pads can be used in several different types of filter – they contain activated carbon which helps to remove chemicals and nasty elements from the water. However, they have a limited life span and have to be replaced regularly otherwise they let the nasty chemicals back into the water.
- Does an external filter need any extras?
If you are going for an external filter system it can be worth investing in a self-priming system which helps to pull the water from the tank into the filter automatically – it just makes it a lot easier and simpler to operate.
- Is it easy to change a filter completely if I get it wrong?
It is possible but it’s not simple. You will need to let the new filter mature first, as when you remove the old one you will be removing all the bacteria. The best way is to run the two filters alongside each other until the new one is mature enough to run alone.
There are many different types and sizes of water filter for fish tanks so choosing the best one for your aquarium is a case of doing some research and making sure you pick the right system for the size of your tank the amount of waste produced.