Fluval C3 vs C4

The first thing to consider when building a fish tank especially after deciding which fish to put together is their filter since this equipment will make sure the water is habitable for our fish. For those with medium aquariums, Fluval C3 vs C4 are two great options from this trusted brand to make sure the water is always clean and reliable enough to let us enjoy some more time before regular maintenance. If you are also eyeing these internal HOB filters, see how they are separated below before choosing.

In this article, we are going to give you information about:

  • Why do you need an Aquarium Filter
  • What are Fluval C3 and C4
  • What Fluval C3 and C4 Look Like
  • How Much are the Capacity of Fluval C3 and C4
  • How Many Filtration Levels do Fluval C3 and C4 have
  • Fluval C3 vs C4

Aquarium Filter

People have different preferences when it comes to pets and we can choose any legal animals to be kept at home, including various kinds of fish. Starting an aquarium project is a fun activity for all ages and genders, but it is also not the easiest thing to do because fish are very prone to discomfort and getting a healthy fish is our first step of getting started. The next steps will be more complicated since depend on the fish, we have to create a suitable environment for them to strive.

When you already decide about which fish to keep and list down their characteristics, perfect food types as well as environment requirement, now we can move forward to selecting the most ideal type of filter for their aquarium. Just like our living environment with soil, water, and trees to help reduce waste being made, fish will also need a type of cleanser to keep their water clean which we call as a filter that can be installed inside and outside the aquarium or fish tank.

Filtration is available in 3 types and since there is no such word as over-filtering, we usually combine all of them to get the best result and clean water for the fish. We mentioned an equipment placed inside or outside the aquarium and this type of filter is called as mechanical filtration. It uses machinery to remove solid particles from water by circulating them and straining it through some kind of media or filter. While it seems powerful, mechanical filter can’t work on its own.

This is where we need biological and chemical filtration because in biological filter we use beneficial bacteria to break down ammonia and nitrite then transforms them to nitrate which is less harmful. For these bacteria to thrive, we need oxygen-rich water and surface like rocks or sand for them to attach to. On the other hand, chemical filtration is done by adding chemical additives to remove and dissolved wastes from the water with the most commonly used is activated charcoal.

When looking for a filter, most of the time we are talking about the first option which is mechanical filter since there are few models to pick between the box or internal filter and canister or external filter like Fluval FX6 vs 406. The rule of thumb is to get the one that fits your capacity since internal filter is most effective when used for aquarium with lesser amount of water while bigger tanks will need a more powerful canister filter that is also more expensive. 

About Fluval C3 and C4

This simple method can help people when looking for the most suitable filter for their aquarium and if you are here, chances the one you need will be an internal filter and only using them for a small to medium sized tank. When talking about a fish tank or aquarium, our mind instantly recall Fluval because they are one of the most popular brands in the market and we are sure many hobbyist are already familiar with this name as well.

Fluval has been in the market for quite some time and the reason why we love this brand is because of their product quality which not only coming in a competitive price but also very reliable in terms of performance with a huge amount of options to choose from. They are currently offering both internal and external or canister filter for people who need more powerful pump to clean their aquariums but if you have fairly small to medium sized aquarium, two of the best options will be their C3 and C4.

The C series from Fluval are made for a smaller aquariums users since they are offered in different capacities and as you can already guess, this line is made with a range of capacity which means most of the capabilities will stay the same except for the capacity because the family start from filter for aquarium as small as 10 gallons working up to 70 gallons which is the upper limit for C4 while the C3 is at 50 gallons.

Fluval C3 and C4 Design

When you open the package and line these two filter together, we can see clearly that the big brother is also comes in a bigger unit because in comparison it is about 2-inch longer, 4-inches wider, and around 4-inches taller which means it also affects the amount of filter surface inside. They are made predominantly from plastic; some parts can come apart and some not depending on the purpose and performance but one thing for sure, the slightly grey, transparent plastic is very durable.

All the accessories we need to run Fluval C3 and C4 are all included inside the box from poly/foam, activated carbon, C-nodes, to Bio-screen pad while both filters are also consuming very little energy at 5 watts. Currently, the price for C4 is around $10 pricier than its little brother yet, at the core they are the same.

Fluval C3 and C4 Capacity

When looking for a filter, the first thing we have to pay attention to is their capacity because it will decide which model we should choose and as it has been mentioned above, what makes these filter different is the size of their capacity because Fluval C3 is made for aquariums from 30 to 50 US gallons and the latter is from 50 US gallons to 70. They actually have the same pump but due to the different in size, C4 is more powerful as well.

This model is offered with filter circulation rating at 264 US gallons per hour thanks to the bigger compartment while the C3 is almost the half at 153 US gallons per hour despite running with the same power.

Fluval C3 and C4 Filtration Level

Both of them are also similarly featured with 5-stage filtration system which covers 2 mechanical filtration 1 chemical filtration, and 2 biological filtration that work hand in hand in shifting out particles as well as cleanse impurities. This is actually what we love the most from Fluval filter including these two models. Their modular media compartment can be taken out one by one easily since there is a handle to pull them outside which in a glance looks like a small basket filled with media. 

This layering level is great when you need to clean them one by one and not all at a time. In addition they are also capable of holding more media compared to many similar hang on back internal filters out there. When you open the lid, there is a tray which is used to hold a filter in which the tray below is also perforated. According to many users this part can get clogged easily so make sure to check this part often.

The second level is a tray filled with ceramic media we used for good bacteria colonization and you may want to make sure there is enough oxygen so these bacteria can do a better job at clearing ammonium, nitrite, and nitrate from your water to be safer for the fish to live. The third layer is what we call as chemical tray and it is coming in red deep pocket that we can pull out with its handle, used to carry the carbon filter pocket.

Some people add another chunks of media above the bagged filter to help the good bacteria but it is custom and we can follow it or not depends on the user’s preference. Fluval is also offering another type of chemical filters for this compartment called the Ammonia Remover in case you want to replace it later. The last panel we can take from Fluval C3 and C4 is their mechanical filter that holds the brand’s poly/foam filter. 

Similar with the other filter accessories, if you prefer another type of material since they can work better, we can also replace it with another filter of your choice as well to capture larger particles and traps finer debris, making sure the water is properly cleansed thoroughly. 


Now, let’s compare Fluval C3 with C4. As it has been mentioned above, these two filters are very similar to each other or actually have the same core but the latter is bigger and capable of taking more media or filters inside so there are more surface and more room for water to flow through which makes it more powerful as well in comparison with the little brother C3.

Fluval C3 vs C4

- Power filter featuring 5 stages of filtration for aquariums between 20 to 50 gallons
- Filters 153 gallons per hour
- Helps provide a stress-free environment; Works to maintain refreshing crisp water
- Equipped with cleaning indicator for when the polyfoam needs to be rinsed


All in all, the decision is all yours to make because not all of us will have the same needs so it is better to get the one that fits your application the most and it is as easy as more water means higher model or those with 50 gallons water and above should pick the C4 while the smaller aquariums will be fine with C3.