Filtration Guide

What is filtration and why is it important?

Filtration is the life-blood of any tank, it keeps the tank clean, keeps the fish healthy, and keeps the water moving and well oxygenated. Overall it almost always the most important piece of tank equipment, this guide will cover what types of filtration there are, what they do, and the types of filters out there and which one is right for your setup.

Types of filtration.

There are three main types of filtration important to every fish tank, biological, mechanical, and chemical.

Biological filtration is by far the most important type of filtration, while some set-ups can thrive without mechanical or chemical filtration, without biological filtration your fish will not survive. 

Biological filtration refers to the nitrogen cycle in a tank (see guide on tank cycling), in short, there are bacteria that live on all the surface area in a tank, these bacteria eat the ammonia produced by fish waste and uneaten food and process it into less harmful chemicals that can be removed by water changes, or live plants. These bacteria live  primarily in the substrate, and filter. They need lots of oxygen to do their jobs properly so a filter with the proper level of flow for the tank size and stocking level is crucial. Along with lots of flow and oxygen these bacteria also need media to grow on, preferably porous materials, many filters come with ceramic rings, or volcanic rock to accomplish this. we recommend Marine Pure Bio-Balls as they are an industry leader in surface area to size ratio and provide an excellent place for your bacteria to thrive.

Mechanical filtration is the filtration that keeps your tank looking clean.

Mechanical filtration is often achieved with sponges or filter pads, the concept is as water flows through these materials any debris in the water column will get caught in the media leading to clear water and preventing the build up of gunk on the bottom and in crevices in the tank. While not strictly mandatory for keeping your fish happy and healthy mechanical filtration does greatly increase the visual cleanliness of a tank. The main drawback is it does need to be cleaned regulfarly, whereas biological filter media should be disturbed as little as possible, mechanical filter media needs to be kept clean so water can flow through it to prevent clogs and keep the water clear.

Chemical filtration is any filter media designed to add or remove any specific chemicals from the water column.

Chemical filtration, like activated carbon, or Seachem Purigen, are usually used to remove chemical impurities from the water, such as medications or chemicals that are accidentally added to an aquarium. We generally do not recommend using them permanently as they don't add much to the health of the aquarium long term and take up valuable filter real estate. That said they can be essential to remove medications from a tank after treating for an illness or ensuring the health of the water column in the case of cleaning supplies or other contaminates accidentally being added to a tank, so are worth having on hand in case of an emergency.

Another less common type of filtration is UV(ultra-violet) lighting. UV lights produce UVC light around 254nm. This light is very powerful and can penetrate the cell walls and membranes of many undesirable organisms in a tank, such as algae, parasites, viruses and unwanted bacteria. It acts as a safeguard against algae blooms, and infections. UV lights should under no circumstances be put directly into, or over an aquarium as the light is incredibly harmful to human eyes and skin, as well as your fish and nitrifying bacteria, it should only be used in enclosed spaces designed specifically for a UVC light bulb.

Types of filters and their benefits. 

There are many types of filters available some better than others, but they all have strengths and weaknesses, this should help outline those and aid in deciding which is right for you and your tank.

Freshwater Aquatics recommended filter types.

Sponge Filters. Sponge Filters are fantastic little devices, the most basic ones consist of a plastic tube surrounded by a chamber then encased in a sponge. They require an air pump to run. The pump pushes air down the tube to the bottom of the filter then as it bubbles up the inner chamber it pulls water in through the sponge and out the top again. The main benifets of sponge filters include lots of surface area for bacteria, as well as mechanical filtration, and of course amazing oxygenation, if your main goal is healthy fish and clear water you cant go wrong with one of these. Sponge filters are also generally one of the cheapest, and easiest to setup and clean filters you can get making them a great choice to be used as the main filtration, or as an additional form of filtration for extra water clarity and oxygen to complement other filters. The main drawback to sponge filters is the lack of customization, they don't have an additional chamber you can add extra media to, so you have to plan accordingly.

Hang on Back Filters. Also called waterfall or backpack filters these filters suck water out of the tank through a tube, push it through a chamber on the back of the tank, then waterfall it back into the aquarium. The main benefits of HOB filters are the ease of access, as well as the customization available a properly sized HOB will push lots of water through your media meaning it filters the entire tank volume thoroughly, the back chamber also allows you to use whatever media type is best for your tank. The main drawbacks to HOB filters are the visibility/location, the noise level, and the lack of quality in many brands. HOB filters take up lots of space both in and out of the tank, they can also be quite noisy, especially as water evaporates and it falls farther out of the filter into the tank. Many HOB filters are produced with very cheap parts especially the pumps and impellers, leading to them failing early into their lifespan, the best way to avoid this is by ensuring that you buy a high quality filter from a reputable brand and seller, preferably one with at least a one year warranty.

Canister Filters. Canister Filters are filters that sit below the tank with an inflow tube and outflow tube going into the tank. Canisters offer the same customization as a HOB but with even more space available, they also take up less real estate inside the tank itself. They also often come with high quality, high power pumps leading to very long lifespans. though it is still essential to make sure your buying a reputable brand with a warranty. The only real drawback to a canister filter is that they are often harder to access for cleaning and adjusting your media than other filters, but this can be mitigated with your filter placement, and the fact that their so large means you often times need to clean them significantly less than other filter types.

All in One/Sump Filters. All in one filters are contained within the back of the tank itself, usually with an overflow leading to your media chambers, then to a pump chamber that pumps water back into the display portion of the tank. They offer excellent customization, as well as keeping all of your equipment hidden and out of the main display, at the trade off of less display space in your tank. A sump is like a mix between an AIO and canister. It is a Seperate tank below the main display that water flows into and is then pumped back out. They allow excellent customization, easy access to your equipment, while keeping it out of the display. The only drawback to a sump is it often times requires drilling holes into the main tank, or buying a tank designed for the use of the sump, increasing the overall price quite a bit.

Other filter types

Undergravel Filters. These filters are largely a thing of the past, having been replaced with more efficient filters over the years, these filters consist of grates under the substrate connected to a pump. They rely entirely on the bacteria in your substrate, heavily limiting your biological filtration, and restricting your mechanical and chemical filtration to small containers. They frequently get clogged and are very hard to access, which is why most reputable fish stores have stopped selling them all together.

Internal Filters. Internal Filters are usually a pump connected to a chamber for media similar to a HOB filter but they are contained entirely inside the tank. They can work well depending on the media used but have the drawback of being hard to access and taking up lots of real estate inside the display.

There are many other styles of filtration available, but these are often designed for more niche use cases if you would like more information about a type of filter not listed here feel free to reach out to use via email or phone and we can provide more in depth information.