Should A Fish Tank Filter Be Fully Submerged?

Fish Tank With Filter
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: November 3, 2023
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Having a good filter is important for keeping your fish tank clean and healthy. If the filtration is not good enough, the water can become dirty and harm the fish. A good filter removes waste and toxins from the water, making it clean and clear for your fish; it also helps to add oxygen and stop bad bacteria from growing. As someone who takes care of fish, it’s important to know how important a fully submerged filter is for keeping your fish happy and healthy. So, should a fish tank filter be fully submerged?

Article Summary

  • Filters serve various functions, including removing physical debris, providing biological filtration, and aiding in chemical filtration.
  • Fully submerging a fish tank filter is recommended for efficient filtration, even circulation, and noise reduction.
  • Cons of fully submerged filters include increased cleaning frequency, potential discomfort for sensitive fish species, space limitations, and accessibility challenges.

Why do I Need a Filter?

Filters are an essential component of any fish tank setup. They play a crucial role in maintaining the overall health and well-being of your aquatic pets. Here’s why you need a filter:

Remove Physical Debris

One of the primary functions of a fish tank filter is to remove physical debris from the water. Internal filters effectively capture and trap uneaten food, fish waste, and other particles that can cloud the water. By doing so, they help keep the aquarium clean and visually appealing.

Provide Biological Filtration

Filters also provide biological filtration, which is vital for creating a healthy environment for your fish. They host beneficial bacteria that break down harmful substances such as ammonia and nitrites that are produced by fish waste or decaying matter. This process helps to maintain optimal water conditions and prevent toxic build-up.

Aid in Chemical Filtration

In addition to physical and biological filtration, internal filters also assist in chemical filtration. They work by removing pollutants like heavy metals or excess chemicals from the water, ensuring a safe living environment for your fish.

Without a proper filter system in place, maintaining optimal water quality becomes challenging. Poor water quality can lead to the sickness of fish (even stress), making it essential to invest in a reliable filter.

Penn Plax Cascade Hang-on Aquarium Filter
Hang-on-Back Aquarium Filter

Different types of filters are available on the market, including external filters (such as canister filters), power filters (HOB filters), and internal filters. Each type has its own advantages and disadvantages based on factors like tank size, desired flow rate, and maintenance requirements.

Remember to regularly clean or replace your filter media according to manufacturer guidelines to ensure its effectiveness. With a well-maintained filter system in place, you can enjoy crystal clear water while providing a healthy habitat for your finned friends.

Understanding Water Levels in Integrated Aquarium Filters

To ensure optimal performance, integrated aquarium filters have specific water level requirements. The correct water level is crucial for the filter’s motor and impeller mechanism to function properly. If the water level is too low, it can lead to excessive noise or damage to the filter components. On the other hand, if the water level is too high, it can result in reduced efficiency or even overflow issues.

Maintaining the appropriate water level in your fish tank is essential for a healthy aquatic environment. Here are some key points to consider:

Proper Functioning of Motor and Impeller Mechanism

Integrated aquarium filters rely on a motor and impeller mechanism to circulate water and remove debris. These components need to be fully submerged in order to operate effectively. When the water level drops below the recommended range, it can cause strain on the motor and impeller, leading to increased noise or potential damage.

Avoiding Excessive Noise and Component Damage

Insufficient water levels can create turbulence within the filter, causing excessive noise that may disrupt both you and your fish. When parts of the filter are exposed due to low water levels, they are more susceptible to damage from debris or accidental contact.

Preventing Reduced Efficiency and Overflow Issues

Conversely, having excessively high water levels can negatively impact the efficiency of an integrated fish tank filter. When there is too much water in the tank, it can overwhelm the filter’s capacity to process it effectively. This may result in poor filtration performance or even lead to overflow problems.

Should a Fish Tank Filter be Fully Submerged?

Sponge Filter Setup in an Aquarium
A Sponge Filter Fully Submerged in an Aquarium

To ensure efficient operation, it is recommended that fish tank filters be fully submerged. This allows the filter to draw in water evenly from all areas of the tank, resulting in effective filtration.

Submerging for Effective Filtration

Fully submerging the filter enables it to function optimally by pulling water through its media and removing impurities. When the filter is completely underwater, it can effectively trap debris, excess food, and fish waste, keeping the water clean and healthy for your aquatic pets.

Inadequate Circulation with Partial Submersion

If you partially submerge the filter, there may be inadequate circulation within the tank. Insufficient water flow can lead to stagnant areas where waste accumulates and harmful bacteria thrive. By fully submerging the filter, you ensure that every part of the tank receives proper filtration and prevents any potential health issues for your fish.

Minimizing Noise

Another advantage of fully submerging your fish tank filter is that it helps minimize noise caused by splashing or gurgling sounds. When a filter is not fully submerged, it may create disruptive noises that can disturb both you and your fish. By immersing it completely underwater, you reduce these unwanted sounds and create a more peaceful environment for everyone.

Pros And Cons

One option that some fishkeepers consider is fully submerging the filter. This approach has its pros and cons, which we will explore in this section.


Fully submerged internal filters have their advantages. Here are some pros to consider:

  • Consistent flow rates: Fully submerged internal filters provide consistent water flow throughout the entire tank volume, ensuring efficient filtration.
  • Effective mechanical filtration: Submerged filters excel at trapping larger particles underwater, resulting in better mechanical filtration and cleaner water.
  • Reduced surface disturbances: For certain fish species, fully submerged filters create less disturbance on the water’s surface, reducing stress levels and promoting a more natural environment.
  • Aesthetically pleasing: Submerged filters are generally hidden from view, enhancing the overall visual appeal of the aquarium by keeping the filter out of sight.


While there are benefits to using fully submerged internal filters, there are also some drawbacks to consider:

  • Increased cleaning frequency: Fully submerged filters may require more frequent cleaning due to debris accumulation underwater, requiring regular maintenance to ensure optimal performance.
  • Sensitive fish species: Some fish may be sensitive to strong water currents created by fully submerged filters, leading to discomfort or stress for these particular species.
  • Space limitations: Certain filter types can take up valuable space within the tank when fully submerged, potentially limiting the available swimming area for your aquatic pets.
  • Accessibility challenges: Fully submerging a filter can make it difficult to access and maintain, especially in larger tanks where reaching the filter at the back or sides might be challenging.

By understanding the advantages and disadvantages of fully submerging a fish tank filter, you can make an informed decision about the best filtration system for your aquatic pets.

Types of Filters And Their Optimal Positioning

Understanding the various filter options available and where they should be placed can greatly enhance the efficiency and effectiveness of filtration systems.

Hang-on-Back Filters

HOB filters are a popular choice for fish tanks. To ensure their effectiveness, it is important to position them correctly. These filters should be placed with the intake near the water surface. This positioning allows for effective skimming action, removing debris and impurities from the top layer of water.

Canister Filters

Canister filters work best when positioned below the tank. By placing canister filters below the tank, gravity can aid in water flow. This helps to create a more efficient filtration system, as water can easily move through the filter media and back into the tank.

Undergravel Filters

Undergravel filters are another type of filter commonly used in fish tanks. These filters are installed beneath a layer of substrate and rely on upward water movement through gravel for filtration. The placement of undergravel filters beneath the substrate ensures that water is properly circulated throughout the tank, providing effective biological filtration.

Sponge Filters

Sponge filters offer versatility in terms of placement within a fish tank. They can be placed anywhere in the tank and provide both mechanical and biological filtration. Sponge filters work by trapping debris and waste particles while also providing a surface area for beneficial bacteria to grow.

How to Set up an Aquarium Filter

Setting up an internal aquarium filter is an essential step in creating a healthy and thriving aquatic environment for your fish. A properly functioning internal filter helps to remove debris, excess food, and waste from the water, keeping it clean and clear. In this section, we will walk you through the steps to set up an aquarium filter, ensuring that your fish have a clean and safe habitat to live in.

Thoroughly Rinse Filter Media

Before placing the filter media into the compartments, make sure to give them a good rinse. This step helps remove any dust or debris that may have accumulated during storage or transportation.

Follow Manufacturer Instructions

To ensure proper assembly and installation of your aquarium filter, it’s essential to follow the manufacturer’s instructions. Different filters may have specific requirements, so be sure to read the manual carefully.

Secure Hose Connections

When connecting hoses or tubing to your internal filter, ensure a secure fit to prevent leaks or loss of suction power. A loose connection can lead to water leakage and compromise the effectiveness of your filtration system.

Prime Your Filter

If required by your specific filter model, prime it before turning it on. Priming involves filling the filter with water to remove any air pockets and ensure smooth operation. Refer to the manufacturer’s instructions for priming guidelines.

Setting up an aquarium filter is crucial for maintaining a healthy environment for your fish. By following these steps and paying attention to manufacturer recommendations, you can ensure that your filter functions optimally.

How Should I Know if The Filter is Working

Aquarium Filter in a Planted Tank
Aquarium Filter in a Planted Tank

Knowing if the filter is working is essential for maintaining the quality and efficiency of any filtration system. Let’s explore different ways to determine if a filter is working properly, providing you with the knowledge and confidence to assess the performance of your filtration system.

Observe Consistent Water Flow

To determine if your fish tank filter is working properly, the first thing you should do is observe the water flow from the outlet of the filter system. There should be a steady and consistent flow of water. If you notice a weak or intermittent flow, it could indicate an issue with the filter.

Check for Unusual Noises

Another way to assess the functionality of your filter is by listening for any unusual noises coming from the motor or impeller mechanism. A properly functioning filter should operate quietly without any grinding or rattling sounds. If you hear anything out of the ordinary, it may be a sign that there is a problem with the filter’s components.

Monitor Water Parameters Regularly

Regular monitoring of water parameters using test kits is essential to ensure stable levels of ammonia, nitrites, and nitrates in your aquarium. These levels should remain within appropriate ranges for a healthy aquatic environment. If you consistently observe high levels of these substances despite having a filter in place, it may indicate that your filter is not effectively removing harmful compounds from the water.

Observe Healthy Fish Behavior and Clear Water

The behavior of your fish can also provide insights into whether your filter is working as it should. Healthy fish will exhibit active swimming patterns, normal feeding behavior, and vibrant colors. Clear water free from debris and algae growth indicates that your filter is effectively removing impurities.

Frequently Asked Questions

How deep should the filter be in a fish tank?

The depth at which a filter should be placed in a fish tank depends on the type of filter you have. In general, for most underwater or submersible filters, you should position them near the bottom of the tank, usually within the first few inches from the substrate. However, it’s essential to follow the manufacturer’s instructions for your specific filter, as requirements may vary.

How should a filter sit in a fish tank?

The filter in a fish tank should sit securely on the substrate or on a designated mounting bracket if provided by the filter manufacturer. Ensure that it’s level and stable to prevent any tilting or displacement. Proper positioning and stability of the filter are crucial for its efficient operation and water circulation.

Can an aquarium pump be fully submerged?

Yes, most aquarium pumps, especially submersible ones, are designed to be fully submerged in water. Submersible pumps are safe to use underwater, and they are commonly placed in fish tanks or sumps to circulate water, aerate the tank, or power various filtration systems. However, always verify the manufacturer’s guidelines to confirm that your specific pump can be fully submerged.

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