Underwater or Above Water? What’s Best for Your Fish Tank Filter

Yes, your fish tank filter should be underwater. A submerged filter allows it to function properly and efficiently while keeping your tank healthy.

Fish tanks are more than just an aesthetic element in a room. They are miniature ecosystems that require careful maintenance to keep the inhabitants healthy. A key element in maintaining a healthy tank is the filter, which is responsible for removing debris, harmful chemicals, and maintaining water flow.

It is essential to use a filter designed specifically for the size and type of your tank and to keep it submerged at all times. A submerged filter ensures proper water flow and prevents any harmful substances from settling on the bottom of the tank. In this article, we will discuss the benefits of using an underwater filter and provide tips on maintaining a healthy fish tank.

Underwater or Above Water? What's Best for Your Fish Tank Filter

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Underwater Filters

If you are an aquarium enthusiast, then you know that excellent filtration is the key to maintaining a healthy fish tank that your aquatic pets will enjoy. One of the options available is an underwater filter. We will discuss the key features, advantages, and considerations of using an underwater filter.

Definition Of Underwater Filters And How They Work

Underwater filters are placed at the bottom of an aquarium and operate by pulling water into the filter through an intake tube. As the water passes through the filter, mechanical filtration removes debris, and biological filtration removes harmful aquarium waste.

The filter media inside the underwater filter also performs a chemical filtration process, which helps to remove impurities such as chlorine and chloramines from the water. The clean water is then returned to the aquarium via an outflow tube.

Here are the components of an underwater filter:

  • Filter media
  • Intake tube
  • Outflow tube

Advantages Of Using Underwater Filters

Underwater filters are gaining popularity among aquarium enthusiasts for many reasons. Here are some of the advantages of using an underwater filter:

  • Affordable: Underwater filters are relatively inexpensive compared to other filtration systems.
  • Space-saving: They are ideal for smaller aquariums, as they do not take up too much space.
  • Silent operation: Underwater filters operate quietly, so they don’t disturb the fish or other aquatic pets.
  • Easy to install: Underwater filters are easy to install, and no complicated setup is required.
  • Easy to use: They do not require complicated maintenance, making them ideal for beginners.

Considerations Before Choosing An Underwater Filter

Before choosing an underwater filter for your aquarium, there are some factors you might want to consider to ensure that the filter meets your needs and requirements.

  • The size and flow rates of the filter: Consider the size of your aquarium and the water turnover rate required to maintain the aquarium’s balance.
  • Type of fish: Different kinds of fish produce different levels of waste, so consider the types of fish you have before installing the underwater filter.
  • Types of filter media: Look for underwater filters that accommodate the filter media of your choice, to ensure efficient filtration.
  • Maintenance: Choose an underwater filter that you can easily maintain without disturbing the aquarium and its inhabitants.

Underwater filters are a reliable and affordable way to maintain the cleanliness and health of your aquarium ecosystem. With this information, you now have a better understanding of their features, advantages, and considerations before choosing one that fits your needs.

Above-Water Filters

Fish tanks are not just decorations, they are a serene and tranquil environment for aquatic life. But a good aquarium setup involves more than just putting water in a container. You must keep it clean and healthy. One key element in keeping your fish tank clean is the filter system.

Should my fish tank filter be underwater? While underwater filters are common, above-water filters might be a better option for your aquarium. Let’s explore the definition of above-water filters and how they work.

Definition Of Above-Water Filters And How They Work

An above-water filter, also known as a hang-on-back filter (hob), sits on the back of your aquarium, hanging above the water level. The filter sucks up water from the fish tank with a long tube and pumps it through the filter, where the water is purified by different types of filter media, before returning the water to the tank.

Advantages Of Using Above-Water Filters

There are several benefits to having an above-water filter in your fish tank, such as:

  • Easy to install and maintain compared to underwater filters.
  • Hob filters have a higher flow rate, which means more water passes through the filter and is cleaned quickly, promoting a clean and healthy environment for your fish.
  • Above-water filters are simple and affordable, without sacrificing quality.

Considerations Before Choosing An Above-Water Filter

Before choosing an above-water filter, consider the following factors:

  • The flow rate of your filter needs to be appropriate for your aquarium size and fish. Too much flow can disturb the fishes, while too little flow can lead to stagnant water.
  • Hob filters require space on the back of the aquarium, so ensure it doesn’t interfere with other equipment like heaters and lights.
  • Above-water filters can be noisy at times, so consider your fish’s sensitivity to sound.

Above-water filters are an easy-to-maintain and affordable option for keeping your aquarium clean and healthy. Consider the factors before buying an above-water filter to ensure you choose the best one for your tank.

Which Filter Is Best For Your Fish Tank?

Are you wondering if your fish tank filter should be underwater or above water? If so, you’re not alone. This question comes up often among aquarium owners. We’ll explore the pros and cons of underwater and above-water filters and give you our recommendation for which filter is best for your fish tank based on your specific needs.

Comparison Of Underwater And Above-Water Filters

Underwater Filters

Underwater filters are exactly what they sound like – they sit underwater in your fish tank. There are a few different types of underwater filters, including:

  • Power filters: These are the most common type of underwater filter. They use a motor to pull water into the filter and push it back out, filtering out debris and waste.
  • Air-driven filters: These filters use an air pump to draw water through the filter media, which helps prevent water from becoming stagnant.
  • Sponge filters: Sponge filters use a sponge to trap debris and dirt in the water, making them great for small or peaceful fish that don’t produce a lot of waste.


  • Effective at filtering waste and debris.
  • Not visible in the tank, so they don’t detract from the aesthetic.
  • Quiet operation.


  • Requires more maintenance since they’re submerged in water.
  • Can take up valuable space in your tank.

Above-Water Filters

Above-water filters sit outside of your fish tank and suck water up through a tube, filter it, and then return it to the tank. There are a few different types of above-water filters, including:

  • Hang-on-back filters: These filters hang on the back of your fish tank and use a motor to suck water up through a tube and filter it.
  • Canister filters: Canister filters sit outside of the tank and use a motor-powered pump to draw water out of the tank, filter it, and then pump it back in.
  • Wet/dry filters: Wet/dry filters work by trickling water over filter media, making it a great choice for tanks with fish that produce a lot of waste.


  • Easy to access and maintain since they’re outside of the tank.
  • Takes up less space in the tank.
  • Can be more effective at filtering water than underwater filters since they have more media.


  • Can be noisy.
  • Visible in the tank and may not look as aesthetically pleasing.

Determining Which Filter Is Best Based On Your Specific Fish Tank Needs

When it comes down to choosing which filter is best for your fish tank, there are a few factors to consider:

  • The size of your tank: Smaller tanks may not have enough space for a large filter, making an underwater filter or smaller above-water filter the better option.
  • The type of fish you have: Certain types of fish produce more waste than others, so if you have fish that produce a lot of waste, you may need a larger above-water filter.
  • How much maintenance you’re willing to do: Above-water filters tend to require less maintenance since they are not submerged in water. If you don’t have the time or desire to regularly maintain your tank, an above-water filter may be the better choice.

Our recommendation is to go with an above-water filter if you have the space and want a filter that’s easy to maintain. However, if you have a smaller tank or want a less visible filter, an underwater filter may be the better option.

Ultimately, the filter you choose will depend on your specific needs and preferences.

Maintenance Tips For Your Fish Tank Filter

Importance Of Regular Maintenance

To keep your fish tank healthy and your fish happy, regular maintenance of your fish tank filter is essential. Here are some reasons regular maintenance is important:

  • Prevents the build-up of harmful bacteria and debris in the filter
  • Maintains water clarity and quality for the health of your fish
  • Increases the lifespan of your filter and saves you money in the long run

Tips For Cleaning And Maintaining Underwater Filters

Underwater filters are commonly used filters in fish tanks. To keep your underwater filter functioning properly, follow these tips for cleaning and maintenance:

  • Turn off the filter and unplug before cleaning
  • Remove the filter floss or sponge and rinse it in warm water
  • Use a soft brush to clean the impeller and housing
  • Check the motor for any signs of damage or wear
  • Replace the filter media every 4-6 weeks to maintain optimal performance

Tips For Cleaning And Maintaining Above-Water Filters

Above-water filters are another popular type of filter used in fish tanks. Follow these tips for cleaning and maintenance to keep your above-water filter running smoothly:

  • Turn off the filter and unplug before cleaning
  • Remove the filter media and rinse it in warm water
  • Use a soft brush to clean the impeller and housing
  • Check the motor for any signs of damage or wear
  • Replace the filter media every 4-6 weeks to maintain optimal performance

Regular maintenance of your fish tank filter is necessary to keep your aquarium ecosystem healthy. Keep these tips in mind for cleaning and maintenance of your underwater or above-water filter, and your fish (and wallet) will thank you in the long run.

Frequently Asked Questions Of Should My Fish Tank Filter Be Underwater

Should I Keep My Fish Tank Filter Underwater?

Yes, placing the filter underwater will allow it to function properly and keep your tank clean. This positioning allows the water to flow into the filter, where it can pass through the filter media to remove debris and impurities before circulating back into the tank.

Can I Place My Fish Tank Filter Above The Water?

Ideally, filters should be kept underwater since the flow of water into the filter depends on gravity. If the filter is above the water, it may not work efficiently. It is also noisier than when it is underwater because of air entering the filter.

How Do I Set Up An Underwater Fish Tank Filter?

First, determine how many gallons of water your tank holds, then purchase a filter rated for your tank size. Install your filter following the instructions provided, typically placing the filter media inside the filter chamber. Once the filter is operational, monitor the water quality.

How Can I Tell If My Fish Tank Filter Is Working Properly?

You can check your filter’s efficacy by monitoring your tank’s water quality. If the water appears cloudy or smells bad, or if you see floating debris, your filter may not be working adequately. You may also notice reduced water flow or noise from the filter.

How Often Should I Clean My Fish Tank Filter?

Filters should be cleaned regularly, not more than once a month. However, the frequency of cleaning will depend on the bio-load of the tank. Observe your aquarium and clean the filter when necessary, typically when flow has slowed or the water has become cloudy or has an odor.


It’s clear now that choosing the correct filter for your fish tank is a crucial element of ensuring a healthy aquatic environment. However, deciding whether the filter should be placed inside or outside the tank is another significant factor that needs to be considered.

After reviewing the pros and cons of placing the filter underwater, it’s evident that an underwater filter may be best suited for certain types of tanks. Adequate research to ensure you match the filtration system to the type of aquarium you have can help avoid any unnecessary expense, frustration, or harm to your fish.

Now, you can make an informed decision based on the form, size, and maintenance needs of your aquarium and your fish. Overall, a creative balance between the mechanical, biological, and chemical filtration systems will ensure that your fish have clean and healthy water, leading to a long and fruitful life.