The most important aspect of filtration for tanks is establishing the nitrogen cycle. However, I will devote an entire page to that subject which you can get to here.
“Filtration” basically refers to the cleaning of water in an aquarium. I use “cleaning” to mean “made suitable for your fish.” Besides adding a water conditioner to tap water, water must be cleaned when it becomes dirty as the fish eat and poop. The water can be cleaned in 3 main ways:
- mechanical filtration
- biological filtration
- chemical filtration
I highly suggest having at a minimum both the mechanical and biological filtration in amounts adequate for your tank size (gallons of water) and stocking (amount of fish in your tank).
Mechanical Filtration
Mechanical filtration gets rid of pieces of yuck, in other words any physical particles, including things such as bits of uneaten food and fish poop. To accomplish this, water is pumped through a porous object such as a sponge. The sponge traps the debris as the water passes through. Sponges also double well for added biological filtration. We will get to more of that later.
Biological Filtration
As fish release waste into the water, ammonia is created. Ammonia is highly toxic to fish and in large quantities is even fatal. Therefore, it is important to have what we refer to as biological filtration to remove any ammonia in the water. This is accomplished through the aforementioned nitrogen cycle. The extremely short version is that there is a set of bacteria which we call beneficial bacteria, which grows on surfaces, which removes the ammonia. Because this beneficial bacteria grows on surfaces, your filter should contain some sort of object with high surface area. This is why a sponge can double for biological filtration. Sponges provide tons of areas for the beneficial bacteria to grow. Keep in mind that the bacteria are living, and when cleaning your tank try your absolute best to avoid killing as many of them as possible. One way you can do this is by keeping filter media (the stuff that goes inside your filter) wet. So biological filtration is the act of pumping water over some beneficial bacteria, and the bacteria will take the ammonia out, leaving your water ammonia free.
Chemical Filtration
Water can become discolored and stinky. In these cases activated carbon can be placed in filters to make water look pristine. Not all hobbyists use activated carbon because it is not essential to the lives of the fish and can be pricey. Carbon pulls in impurities but can only hold so much. After about a month of use it must be replaced. Because it is not absolutely essential, must be replaced every month, and can be pricey some don’t use it. Personally, I use activated carbon. Many filters come with cartridges of activated carbon which can easily be replaced. They also conveniently sell new cartridges to replace the old ones… A six month supply of cartridges for my filter costs between $12-15. That is for a 10 gallon tank. As the tank gets bigger, so does the price tag on the cartridges. The maker of my filter offers a year’s supply for the same price as six months, but those require some assembly. Another option is to buy a reusable pouch and buy carbon in bulk and make your own cartridges entirely.
Filters
Now that we have looked at the different types of filtration, let’s look at some different filter options. All of the following filters support both mechanical and biological filtration. Due to time restraints, I will not be able to fully flush out every type of filter. However, over time, I will get to all of them. I promise 🙂
- sponge filter
- hang on back (hob)
- internal (coming soon)
- canister (coming soon)
- sump (coming soon)
- under gravel filter (coming soon)
Sponge Filter
Sponge filters are one of the most basic, inexpensive, yet effective filters. Basically a weighted sponge sits at the bottom of the tank. A airline runs down and connects to the sponge, pushing air down into it. As the air exits the sponge and heads toward the surface, it pulls water up through the sponge. The sponge catches any debris in the water while also filtering it biologically with the bacteria that grow there.
As with any other type of filter, there are a few cons. First of all, sponge filters aren’t, well, pretty, to look at. They can also be a bit bulky and therefore difficult to hide behind decorations. Secondly, they are powered by an air pump which can vibrate loudly when placed on a hard surface. Thirdly, sponge filters have no place for activated carbon.
On the bright side, they are inexpensive, they are effective, and the power source can easily be switched out in case of a power outage.
Hang on Back
The hang on back filter literally hangs on the back of the aquarium. The intake valve and water return sit inside the aquarium while the filter mechanism sits outside the aquarium wall. Thus it literally, hangs on the back, half in and half out of the aquarium.
A pump causes water to flow up the long tube, through the filter, and out the other side, which often is built as a little waterfall.
Between the intake tube and where the water comes out, is where you place your filter media. Many people include sponge/foam (mechanical), carbon cartridges (chemical), as well as other biological media such as more sponge or pre-made high surface area pieces of plastic cut to the dimensions of your filter.
Pros: hobs often come in aquarium starter kits and can be easy to maintain because most manufacturers pre-make replacement carbon cartridges. Furthermore, because the majority of the filter sits outside the aquarium, your fishy will have more room to swim. They are also very quiet-usually much quieter than the air pump of a sponge filter. Another nice thing is that you can really individualize the filter medial you decide to put in. Some people will even add a sponge onto the intake valve (this can be seen in the first picture).
Cons: hobs are very visible, thus making it more difficult to hide and create a more natural looking aquarium. Also, if you decide to use the carbon cartridges, you must replace them every 3-4 weeks. These also do not have enough room for the heater. In the larger filters, some people choose to place the heater inside the filter, thus creating more swimming space and one less piece of ugly equipment in the tank.
Finley's Journal 