A sparkling clean aquarium is a captivating sight. Have you ever become fixated on the interplay of light and shade, the slight swaying of the plants and the swimming of the fish, all within an environment that appeared to be radiating with its own intensity? An aquarium can act like a portal to another world, one which we as land dwellers rarely have access to encounter. But a dirty aquarium can dull the effect of this amazing sight, in addition to harming the aquatic life within.
So how do we keep the water clean in appearance as well as in actuality? The filter, in combination with regular cleaning, is the answer!
Here we will examine the three types of filtration methods for the aquarium, and how to choose among the various options available.
Table of Contents
The Mechanical Filter
When most people think of an aquarium filter, the mechanical filter is what comes to mind. It is the most popular choice for freshwater aquariums, and is a great way to get started as a beginner aquarist.
As the name would suggest, the mechanical filter runs water through a medium, allowing it to pass through while trapping the larger waste particles before they get lodged on or under the substrate.
The media through which the water passes could be a sponge, a filter pad, or filter floss. It can be fine, medium or coarse, which means the pores range in size from small to large. Fine media traps more but can also become clogged easier than coarse media, even potentially trapping oxygen. Some aquarists use both coarse and fine filters one after the other, so that the coarse media keeps the large particles from clogging up the finer one.
Regardless of which media you use, it is important to clean it regularly every two weeks. Replacing the media every 3-6 months is also recommended.
The Chemical Filter
Some filters rely on chemical reactions to remove harmful elements from the water. There are many ways to target specific substances that you want to remove from the water, such as phosphates, ammonia and heavy metals.
Among the most popular of these filters are active carbon, charcoal, zeolite, oxide and resin.
So where are these materials placed? They are placed inside the filter itself as the media. Take a canister filter type as an example, which contains multiple compartments for placement of media. You simply place the chosen material into one of the trays or compartments, usually after it passes through a mechanical filter media like a sponge.
Remember to regularly test the water parameters to make sure there are no big changes occurring. Chemical media can eventually become saturated with the waste and chemicals it absorbs, causing it to fail in its effectiveness and even potentially release some back into the water. Choose a material based on your needs, but make sure you know how long the lifespan generally is before it reaches capacity. Then it’s time to replace.
The Biological Filter
This type of filtration happens largely on its own, because you have little helpers available called nitrifying bacteria. All they need to live is an oxygen-rich environment and a place to which they can attach themselves. Your job, then, is twofold. Firstly, keep the water oxygenated through regular cleaning of the filter as well as water changes. And secondly, give the bacteria plenty of places to live.
These bacteria can live on almost any hard surface, but giving them plenty of substrate, aquarium decorations and even filter media allows them to flourish in large numbers.
There are some products called bio media which you can purchase specifically to provide additional living space for such bacteria, including ceramic rings, bio blocks and bio spheres. These can be placed inside a filter to facilitate the passing of water over these beneficial bacteria colonies.
Allowing these bacteria plenty of space to live will improve the nitrogen cycle, which happens in two steps: one type of bacteria breaks dangerous ammonia down into nitrites, and the other type breaks nitrites down into nitrates. Nitrates are much less harmful to fish than the first two mentioned, and they even benefit plant life which takes it in and releases oxygen back into the water…a complete cycle!
What Type of Aquarium Filter is Best?
Now that you have an understanding of the different ways of filtration, how do you set this up practically? Let’s take a look at the options available so we can make an informed decision on what to do next.
Hang-on-Back Filter
Also known as the power filter, this is by far the most popular filter for beginners. They are easy to install, simple to use, and will do an excellent job at pulling the visible waste out of your water. These hang behind the aquarium’s back wall and can utilize all three filtration types: mechanically filtering with a sponge or floss media, chemically filtering with activated carbon, and biologically filtering with the bacteria that grows on the aforementioned media.
Sponge Filter
The sponge filter is also very popular because it is so simple. It consists of a sponge which sits inside the tank and a tube which sends the water inflow up to the surface for outflow. Used in conjunction with an air pump which sits outside the tank, water is pulled through the sponge so that debris is trapped and clean water is released up through the tube. This does not create much of a water current, making it particularly attractive for breeding tanks since the small fry won’t be accidentally caught in the suction. The sponge also gives bacteria a place to live and break down harmful substances. This doesn’t allow for chemical filtration so is sometimes used in conjunction with other filters.
Internal Filter
How about keeping the filter underwater? This eliminates the need for tubing that pipes water above the surface level. Internal filters are best suited for small to medium-sized aquariums (up to around 40 gallons) and usually are placed in a back corner either by hanging onto the top or suctioning onto the wall. This can offer all three types of filtration and also serves to keep the water circulating and aerated (benefiting oxygen levels). The downside is that it takes up precious space in the aquarium and is visible to the observer. It is a cheap option of filter, but also does not usually perform quite as effectively as the external filter.
Canister Filter
If you want to go next level with your filtration, try a canister filter. This consists of a much larger container that sits entirely separate from the aquarium, connected by two hoses (inflow and outflow). It contains several layers through which the water will pass before being returned to the aquarium. This gives you ample space and opportunity to add a number of media.
It’s important to note which way water flows in a canister filter, as some models push the water from bottom to top, whereas others move top to bottom. This matters, because it’s best to put the mechanical media as the first layer through which water will pass, effectively trapping large debris that could potentially clog up in the other layers. Usually this is followed by chemical media and finally with biological media, possibly with one more mechanical filter before returning the pristinely clean water to the aquarium.
These can be excellent for larger aquariums, anywhere from 20 to 200 gallons. Downsides are that they are expensive to purchase and difficult to clean, also having been known to spring leaks from time to time. But if you’re comfortable with the maintenance, these can filter a lot of water very effectively.
Undergravel Filter
In special instances, you may be able to entirely conceal the filtration process from view by using an undergravel filter. The main benefit is its ability to hide under the gravel. It sucks water and waste down through the substrate, helping to spread the growth of beneficial bacteria throughout the substrate. It then sends the filtered water through the uplift tube to the water’s surface to return back into the tank. The problem with these is that they cannot be cleaned without basically removing everything from the aquarium. The best way to keep these clean is to regularly vacuum the substrate. These are best suited for small tanks, as well as quarantine or breeding tanks.
Trickle Filter
Also known as a wet/dry sump, this is a multi-chambered filter that can be placed on top of, underneath, or beside the aquarium. The term “trickle” comes from its unique characteristic of spreading the water across a plate dotted with holes, causing the water to rain or “trickle” down onto the media filter below in equal quantities. This distributes the water over either the biological or chemical media you choose to place in the filter before pushing the water through a sponge to trap any remaining waste. It is then pumped back into the tank. Interestingly, you can actually hide some equipment in this type of filter, such as the water heater or air stone. While it is more expensive and complex than other filters, it also is very effective and can usually go a month between cleanings (other than the sponge, which is better cleaned every 1-2 weeks).
Conclusion
Now you know the most popular filtration methods and systems used for the aquarium. Not only does the filter assist in cleaning the aquarium, but it also can be used to add important qualities to the water by including certain materials that affect water parameters. Multiple filters can be used in the same aquarium, so long as you are mindful not to create a water current that disturbs your fish. The filter is your best friend when it comes to keeping the water clean and clear. As with most things, the best filter will depend on your specific needs. Simply choose the one which fits the vision for your tank, and watch your fish flourish in the beautifully clear water which results!