External Filter Vs Cascade Filter

If you are new to aquariums, you may be wondering what type of filter is best for your fish tank. When I started out many, many years ago, I only used the filter that came with my tank, which was a backpack filter. Over the years, I realized that there was more to it than just that type of filter. I noticed that a lot of people were using external filters, so I started pondering the differences and trying to figure out which one was better: External Filter VS Cascade Filter

The main difference is that waterfall filters simply hang on the back of the tank and filter the water through a tube. External filters are a bit more complicated and require more time and energy to set up and maintain. Fortunately, there are benefits to each and fully understanding them is a big step in determining which one is best for your tank.

Comparison of external filter with cascade filter

External Filters waterfall filters
  • Cleans the tank more efficiently
  • Requires more installation and maintenance effort
  • No loss of water or fish
  • Can cost much more than a power filter
  • Not as powerful as boats
  • Easy to install and requires little maintenance.
  • Leaves the aquarium open to loss of water and fish.
  • Affordable

Cascade Filters

Power filters, like I said earlier, hang on the back of your fish tank and come in various sizes and shapes. They will usually come with your fish tank if you buy a kit from the store. These are the easiest to use and usually the cheapest.


Power filters simply plug in, have a carbon filter pad placed inside, turn on, and you’re good to go. The internal pump then draws water from the tank, through the riser tube, and then through the filter cartridge. This cartridge contains the proper chemicals needed to keep your water pure and clean. Although the interior may differ from brand to brand and model to model, they are generally very similar in function.

Once the water has passed through the filter media, it is released back into the tank through a spill or overflow. Unfortunately, since the water hits the air on the way back, there will be quite a bit of evaporation, meaning you’ll have to replace the water more often than with an external filter.


Maintenance of power filters is much easier than cartridge filters. With power filters, all you have to do is remove the carbon filters or other type of media depending on the make and model you have and replace it. It is not necessary to remove the filter from the back of the tank unless you suspect something is wrong with the tube that is sucking in the water.

It’s also not all the time you have to replace the filter. If you are doing a water change and the carbon filter is not ready to be changed, you can simply rinse it out and replace it. Once you’re ready to change, just change it.

Canister filters, on the other hand, are much more difficult to clean because they must be disassembled, drained, and reassembled without disturbing any of the natural bacteria in the facility. This means that the process must be done quickly and meticulously, ensuring that your fish are not killed.

What should you be aware of?

Power filters may seem like the optimal choice because they are easy to operate, require minimal maintenance, and are really inexpensive. Unfortunately, they can be really inefficient. The reason is that the intake is usually directly below the weir. Since the water being returned is directly below the weir, much of the water entering the filter is actually clean water that has just been returned to the tank.

losing water

Power filters also lose a lot of water in the process between cleaning and returning the water to the tank. Like I said earlier, since the water is exposed to air on the way back, evaporation is highly recommended, meaning you’ll lose a significant amount of water. However, this is not always bad. Since there is an increase in surface area with these filters, dissolved gas levels will improve. This keeps the oxygen for the fish closer to the amount available in the air.

lose fish

Since you need a fairly large opening in your tank to accommodate the power filter, this creates an escape route for your fish if the water gets too high. This also applies to any amphibians or crustaceans you have in your tank.


Power filters are very affordable. Most of the time, they come with your aquarium setup. If you need to buy another or one for the first time, you can expect to pay anywhere from $10 to $50. The $10 range ones are generally the most for smaller tanks like 5-10 gallons. For these I would recommend the Marina Slim Filter. The $50 ones are for the largest tanks, usually between 50 and 100 gallons. For these I would recommend the Fluval C or the AquaClear.

outer filter

Canister filters are much more reliable when it comes to filtration for saltwater and planted aquariums. They also work equally well for freshwater tanks. These types of filters are located outside the tank and use hoses submerged in the tank to filter the water.

These filters are usually not the choice for beginners because they require quite a bit of knowledge to set up and maintain. They are not like power filters that can simply be plugged in and placed in the tank. These require hoses, biological filtration, routine cleanings, and are quite expensive.


Canister filters have tubes that are submerged in the tank. The water is drawn through a riser tube and into an external filter chamber where the water is taken through a few different filter media to clean the water. Depending on the brand of filter, the direction of the water can be from bottom to top, top to bottom, back to front, outside to inside, or center to outside.

Depending on the media you use, the filter media can provide biological, chemical, and/or mechanical filtration. Once the water passes through the filter media in the sealed container, it is put back into the tank through the pump. All boats use pumps to transport the water as the system is sealed. Most cartridge filters come with integral water pumps that are built into the cap or base. Although, some require a separate external water pump.


The maintenance of these filters can vary depending on the model, the brand and the medium used. You can put a variety of filter media in your canister, such as baskets, insulated chambers, media bags, and cartridges. You can use them separately or with each other to provide your tank with the right type of filtration for your particular setup.

Some of the media require you to rinse it regularly rather than when you see it has stopped filtering properly with a power filter. Some of the media also require replacement from time to time, which could cost you a pretty penny. You will also need to clean the tubes, which can be done with tube cleaning kits. Look at this video. It shows you exactly how to clean an external filter and what exactly goes into maintaining one.

Sure, maintaining these filters can take more effort than power filters, but when it comes to the health of your fish, it can be worth it.

What you should be aware of

Canister filters give you more options than a power filter offers. By this, I mean that you have more options to choose from when it comes to your filtration and media. Power filters come with the manufacturer’s pre-made media cartridges. You can mix and match, making sure your fish and other aquatic creatures have the proper filtration they need.

losing water

Since canister filters are not near the top of the tank and the water returns through a spray bar, there is a reduction in evaporation and runoff. You don’t have to worry about the water splashing back into the aquarium through the weir or simply evaporating due to being too close to the surface.

lose fish

The same concept applies to fish loss as it does to water loss; You do not have to worry about that. Since there is no opening at the top of the tank, there is no reason to worry about fish jumping out. They will stay safe inside the tank with the top closed, as the filter does not require an open top.


Unfortunately, cartridge filters don’t come cheap and that’s why some people just stick with power filters. When you buy a tank, a boat is not normally included. These filters can cost you anywhere from $20 to over $300 for a high performance one.

Honestly, I’d spend the extra money even on one for a smaller tank, like the Penn Plax Cascade. This filter can accommodate aquariums between 30 and 200 gallons, depending on which one you choose. If you have a fairly large tank and want only the best, go for the Fluval Fx. This can accommodate aquariums up to 400 gallons.


As you can see, each of these filter types offers its own benefits and concerns. Honestly, if you have the money and the patience, I’d go for the external filter. They require more effort and maintenance, but will keep your tank in better condition than a power filter. Don’t get me wrong, there are very good performing power filters on the market, but honestly, nothing compares to an external filter, in my opinion. Not only that, but you have more options for mid filters than with power filters.

I hope you liked this article and if you have any questions, leave us a comment.

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