Although it is easy to simply purchase an aquarium kit, many of us choose to build our own set-up piece by piece. When this is the case, one of the most important decisions to face is which filter to use. Since this is where a majority of your ammonia processing bacteria live, choosing the right filter may decide whether your tank will struggle or thrive in the future. Though many different brands exist (and those will be covered later) we will begin by discussing the different types.
Hang On Back Filter
The most common type of filter you will see within an “Aquarium Kit” is a hang on back filter. As the name suggests these filters simply hang on the back of your aquarium and have a snorkel which sits down into the water. Within the snorkel the water is pumped up and out of the aquarium, through filter media, after which it waterfalls back into the tank.
In order to set up a hang on back filter you simply hang the filter on the lip of the aquarium(typically on the back side) so that the snorkel is in the water, and the large reservoir on the opposite side is on the outside of the tank. Included with most of these filters is a single filter cartridge that is to be inserted into a slot within the reservoir. Then you fill the reservoir with water from the tank, followed by plugging the unit into a wall. An important note to make is that running the filter without water completely filling the reservoir may damage the pump and this is to be avoided.
These pumps work moderately well, but it is good to remember that the hang on back filters included with kits often have pumps which are the bare minimum for the tank size advertised. This means that if you have a particularly “dirty” fish, such as a goldfish, these filters may be unable to keep up with the waste. As such, a general rule of thumb when choosing one is to have a pump capable of moving 4 times the amount of water in the tank every single hour. This will ensure that any harmful chemicals and unsightly debris will be processed by your filter before anything can happen to your fish.
The primary issue with hang on back filters is the standard filter cartridge which are supplied with these filters. These cartridges are typically very thin and filled with carbon. The manufacturers typically suggest changing these out every month. Instead of using these cartridges you may want to simply replace them entirely with a sponge that fits in the back of the filter. When choosing a sponge, ensure that it is not pre soaped or manufactured with any other chemicals on it meant to help you clean, since these will harm your fish. It is also important to choose one that fits snugly within the filter to guarantee the water has to flow through it instead of around. In addition, placing a “prefilter sponge” around the snorkel of the filter will help prevent any large debris from entering the filter where it may cause the unit to clog. These simple modifications turn the hang on back filter into an ammonia processing machine by creating many sites for bacteria to colonize.
A less common filter, but the one that I personally prefer is a sponge filter. Sponge filters are quite simply large, circular sponges with a hole carved out of the center. In order to set up a sponge filter simply connect the airline tubing to the top of the sponge and the other end to an air pump. Set the air pump on a stable, level spot near the aquarium, then lower the sponge into the tank with the weighted side down. Finally plug the air pump into a power source and the process is complete.
These filters work by pumping air from the surrounding room into the tank where it quickly tries to rise up to the surface. In traveling to the surface (especially if the sponge filter has a lift tube) the air causes water to rush up with it. This creates flow from the sides of the filter, up through the top. Although these filters do not create as much flow as a standard hang on back, the sponge does a fantastic job of hosting the beneficial bacteria which keep your aquarium chemically clean.
In addition to being simple to set-up, these filters are very cheap and easy to maintain. Instead of pulling a dirty filter out of the hang on back and throwing it away you simply pull the sponge filter out of the water,
unplug the air pump, and squeeze the sponge out several times into clean dechlorinated water until the water leaving the sponge runs clear. After this you can simply place the filter back into the tank and plug the pump back in and you are ready to go again. Because of their ease of use and low cost, these filters are by far my favorite.
Canister filters come in all shapes and sizes but they typically work best for aquariums up to approximately 200 gallons. These filters are good for fish that need a higher flow and are typically considered a “dirty” fish. People who favor canister filters do so because they typically only require cleaning approximately once every three months. The downside to this is that after three months there can be a lot of built up debris which can make cleaning a smelly, dirty job.
Canister filters are relatively self contained units. They consist of a canister (which looks similar to a small trash can) that houses all of the filter media as well as the pump which runs everything and two hoses that lead from the filter to the aquarium. One of the hoses will have an end similar to the snorkel seen for a hang on back that prevents large debris and fish from getting pulled into the canister. The other hose which directs water back into the aquarium has a variety of attachments which change the flow of water as it enters the tank. Inside the canister itself are several trays which house the filter media. Depending on the brand and size of canister this media will vary greatly, but I typically use a cleaning floss and sponge first to filter out large debris followed by the material which hosts the beneficial bacteria. In this way I make the water look nice, and ensure it is cleaned properly before returning to the tank.
In order to clean the filter there are two flow restrictors which are closed completely after the canister is unplugged to prevent gravity from siphoning the aquarium onto the floor. The hoses are then removed, the canister is opened, and the various media is cleaned according to the type before being reinstalled. Similar to the hang on back filter, the filter must again be primed (in this case by using a built in hand pump to fill it) then powered back on.
I personally don’t have many fish which need the higher flow levels and cleaning abilities a canister filter provides so I typically stick with hang on back and sponge filters. With that being said, if I ever have a more demanding fish in a larger tank, I will definitely use a canister filter despite its higher price tag. Ease of use is important to me, and these filters provide that to a level no other filter can compete with.
If you have a bigger tank (75+ gallons) then a sump filter may be the right choice for you. There is a certain point where hang on back and sponge filters simply do not have enough power and for these situations a sump filter really shines. A sump filter is basically another tank which rests underneath your main tank and holds all of the filter media required to keep the water clean. Similar to a canister filter, this filter material varies greatly depending on which brand of sump you buy or, for those brave enough, whatever you choose when you make one yourself.
Sump filters are typically one of the least intrusive filters you will find. Instead of having tubes hanging into your aquarium, a hole is typically drilled into the side allowing water to flow out once it reaches a chosen height. The water then flows down a tube which connects to the sump itself which will rest inside the stand of your aquarium. Here the water passes through a large debris filter before flowing through bio balls or ceramic rings where the bacteria chemically convert the ammonia. After these steps the water flows to a final compartment where a pump returns it back to the aquarium. The setup is very similar to a canister filter, but lacks the higher pressure through which the water flows in a canister.
The largest tank I personally own is far too small for me to require using a sump which is why I favor sponge filters, but if I did have a several hundred gallon tank this would be the filter I would choose. I’ve worked with these filters many times before and in addition to being very easy to clean they stay hidden. Sumps also process large quantities of water and I would have much less worry about ammonia spikes when using one.
Under Gravel Filter
The reason this filter is last on this list is because it used to a very common filter but has fallen out of favor in recent years. With that being said, it’s possible you may have been given one of these filters or decided to pick one up when you were at the store and just want to stick with it.
The idea behind the undergravel filter is to use the aquarium substrate as the filter media by pulling the water through it, up a lift tube, and return it at the top of the tank. In order to set up an undergravel filter you must do so before any substrate is in the tank. The filter itself consists of a filter tray which covers the bottom of the aquarium and 1 or more lift tubes. First insert the large tray into the bottom of the aquarium and attach the various lift tubes to the tray. Some lift tubes require more construction than others, but this varies by brand. The general idea of the lift tube is to connect them to the filter tray and have an airstone on the inside of the tube to provide lift. After the lift tube is attached securely to the bottom tray, a large substrate such as gravel can be poured into the aquarium and the air pump can be turned on.
One problem with undergravel filters is that a large amount of debris builds up within the gravel itself. This requires more frequent gravel vacuuming than a standard tank. In addition, the one or more lift tubes within the tank can be rather unsightly since they are often an opaque white plastic which extend from the bottom of the aquarium all the way to the top. Some of these tubes also seem to be perfect hosts for rogue algae (depending on their color and the type of plastic used). Despite these negatives, I do believe the undergravel filter does a good job of keeping the aquarium clean. I just personally would rather have a modified hang on back or sponge filter.