Where to Place Intake and Output of a Canister Filter?

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A reliable filtration system is necessary for any aquatic setup. The filter will heat the environment, oxygenate the water, eliminate debris and dead matter, and provide water currents for your fish to enjoy.

Canister filters are some of the most used pieces of equipment thanks to being easy to use, clean, and maintain. Unfortunately, mounting a filter sounds deceptively simple to an uninitiated.

As a novice aquarist, you only realize the challenges coming with it after getting the filter. So, let’s get into that!

Cannister Filter Intake and Output Positioning Tips

So, you got your filter, unpacked it, and got stuck with the pieces in hand. How do you mount the filter on your tank?

You essentially have 2 options to consider. Which option you choose depends on your tank’s size, shape, and layout.

Same Side Placement

Many people place the intake on the same side as the output. This is more fitting for smaller tanks since the resulting water flow will easily cover the entire system.

The water currents will form a circular motion through the tank, ensuring optimal movement and nutrient, heat, and oxygen distribution.

Naturally, you should tweak the power of the output, especially if you’re running a planted tank. Placing the intake and the output on the same side can quickly overwhelm a system with vulnerable and delicate plants.

However, keep in mind that placing the intake and the output on the same side only works for smaller systems. That’s because the water can quickly traverse the environment from one end to the other.

This setup won’t work for larger and wider systems since the water flow isn’t sufficient to cover the entire area.

What you’ll get in that case are uneven oxygen distribution, dead spots, and uneven water currents.

Some areas will have stronger water currents, while others won’t have enough. This takes us to our second option.

Opposite Side Placement

This method is more fitting for larger systems. The goal is to place the intake and the output in the ideal areas to ensure optimal debris cleaning.

Organizing the filtration system this way ensures optimal water flow and an even distribution of currents, oxygen, CO2, and heat.

Naturally, the system’s effectiveness and reliability depend on the tank’s layout. You don’t want your intake or output close to your plants or more sensitive decorations.

A powerful-enough current could unearth plants, rupture stems and leaves, and tip over various decorations. They can also blow the substrate away, causing the filtration system to produce more problems than it fixes.

4 Things to Consider When Setting Up Canister Filter

Now that you know how to determine your filter’s ideal placement let’s check the factors that should influence your decision.

The concept of a canister filter is simple – the intake sucks in water from the tank while the output source pours it back after filtering it through the system.

Easy enough. However, several factors will influence the placement of these pieces, such as:

1. Heat Distribution

Cannister filters don’t heat up the water. If anything, they will cool it a bit due to the movement and agitation it causes.

So, you should ideally mount a heater onto the filter’s output to heat the water to the ideal values. In this case, the output’s placement will influence both the water’s circulation and its overall temperature.

An uninspired placement could lead to uneven heat distribution, causing hot and cold spots around the tank. This will cause the fish to become more stressed in the process.

And we all know that stressed fish are often sicklier since their immune system drops in the process.

2. Adequate Plant Nutrition

Plants require minerals and other nutrients like CO2, which is being produced in the tank.

The thing is that these nutrients traverse the environment under the guidance of the existent water flow.

If your plants live in an area of the tank with little-to-no water flow, they might not get the CO2 they need.

It takes some guided water movement to stir the CO2 around, making sure that it reaches all corners of the tank.

3. Adequate Oxygenation

The oxygenated water from the filter should move freely through the entire habitat. It’s not necessarily a vital issue if it doesn’t, since the oxygen will eventually spread through the entire tank.

But the fish will sense the difference in the oxygen levels around them and will crowd the areas with more oxygen.

This will lead to territorial fights and even fish waste accumulating in one spot. An even oxygen distribution will prevent these issues.

4. Avoid Dead Spots

Dead spots are areas where there are no water currents. As a result, these zones will accumulate most of the dirt, fish waste, food leftovers, and dead organic matter.

The lack of water circulation in those areas will prevent the filter from cleaning the residues, causing ammonia and nitrite spikes over time.

It’s astounding to see how the filter’s placement will influence the system’s health and stability. Remember, the filter’s entire purpose there is to remove waste and organic matter from the tank.

If your filter cannot fulfill that task reliably by the virtue of poor placement, the system’s very existence is rendered nearly obsolete.

These are the core factors that should influence the placement of your intake and output. Naturally, the esthetic aspect of it also comes into play.

Feel free to experiment in this sense a bit, so long as you don’t sacrifice the utility aspect in the process.


The canister filter is a vital piece of equipment that will keep your aquatic setup fresh, clean, and well-oxygenated.

However, as you’ve just seen, getting and mounting a filter isn’t enough to get the job done. How and where you mount it also makes quite the difference.

As a final note, there isn’t really a strict checklist to follow. Only use this article as a guiding journal rather than a must-follow sketch.

How you place your filter’s intake and output depends strictly on your tank’s overall layout.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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