Under Gravel Filters – Are They Still Relevant?

Under gravel filters, sometimes called UGFs, are one of the oldest aquarium filter types in the business. However, some aquarists are concerned that these filters aren’t all that they’re cracked up to be. Others swear by under gravel filters to keep their tanks properly maintained. 

So, how are you supposed to decide whether or not an under gravel filter is the right pick for you and your fish? Below, we’ll delve into common under gravel filter FAQs along with some general maintenance tips so that you can make the best decision for your tanks. 

under gravel filters

Why Do Aquariums Need Filters?

When it comes to building your dream aquarium, you’ll need to find a high-quality filter of some sort. Essentially, a filter removes excess food, debris, decaying organic matter, fish waste, and any other unnecessary contaminants from the water.

This is important because these contaminants can make it difficult for your fish to survive. Debris build-up can create toxic ammonia and nitrate deposits. From these unbalanced water conditions, your fish may develop a weakened immune system which can be life-threatening, in some cases. 

Therefore, one of the first things you’ll want to invest in is a filtration system. In general, there are 8 different types of filtration systems. 

Types of Aquarium Filtration 

In order to gain a full understanding of the advantages and disadvantages of under gravel filter, it’s important to have a brief overview of how each filtration system works. Here are the 8 most common types of aquarium filters and how they work. 

  • Box Filters

These filters are also called box or corner filters. Box filters are filled with filtration mediums like zeolite that helps absorb ammonia or other harmful water contaminants. These filters are mainly used for small tanks, usually containing of 20 gallons of water or less. Box filters are also great for tanks that have small fry or fish that may be negatively affected by a filter that is too powerful. Some box filters will also require an air pump and line so that water can move through the filter as needed. 

  • Canister Filters

These powerful filters are most common in tanks that are 50 gallons or larger. One benefit to canister filters is that they’re placed outside of the tank. Notably, these sturdy filters provide chemical, biological, and mechanical filtration with ease. 

Canisters filters are pretty powerful and are fully pressurized so that all water is actively filtered. You can also add a biowheel to canister filters to make them more well-equipped for biological filtration. These filters work well with tanks that have live plants as well. 

While these filters are effective, they can be difficult to take apart and clean.

  • Diatomic Filters

Diatomic filters are not stand-alone filter solutions. These filters are only used every once in a while and for a specific purpose. The filters remove minuscule particles, substances like diatomic algae. You’ll find that some filters have diatomic inserts built-in just in case. 

  • Power Filters

Power filters are probably the most common modern filter you’ll find today. These filters can provide large and small scale mechanical, chemical, and biological filtration. The filter hangs off the back of the aquarium tank and sucks up water through a specialized tube. You can also customize power filters with a biowheel to increase biological filtration efficiency. 

  • Fluidized Bed Filters

These biological filters are placed on the back of the aquarium and use sand or silica as a medium. You’ll need to have a water pump to utilize this modern filtration method. These filters create a healthy environment to breed biological filtering bacteria. 

  • Sponge Filters

Sponge filters work by promoting the growth of healthy bacteria that induce natural, biological filtration. The sponge is used in conjunction with a powerhead or air pump. These filters need to be monitored carefully in case of excess debris or contaminant build-up. Always clean your sponge filter with aquarium water— Tap water can kill off the helpful bacteria that these sponges work to create. 

  • Trickle Filters

Trickle filters are sometimes called wet and dry filters and work to expose water to air. Exposure to the air through a filter medium can make it easy for beneficial bacteria to build-up in your tank for biological filtration. You can also use different filter media to help facilitate chemical filtration as well. 

  • Under Gravel Filter (UGF)

The under gravel filter is one of the most classic filter types that is placed beneath the substrate of the tank. UGFs can be great for biological filtration because they make it easy to filter the entire bottom of your tank. 

Fighting Fish, Betta, Aquarium, Fish

Why Would You Use An Under Gravel Filter?

In general, under gravel filters consist of four main parts:

  • The perforated plate that sits under the gravel itself
  • Uplift tubes
  • Water pump 
  • Air pump

The filter is designed to pull water through a substrate type, trapping excess debris and dirt as water passes through. These filters are relatively simple and usually quite affordable. While they can be very effective, they require regular maintenance in order to run properly.

If an under gravel filter isn’t maintained properly, your substrate can collect a high level of debris which can be toxic for your fish on its own. In addition, you’ll need to make sure that you regularly clean your substrate (as you would with any filter) to keep everything in tip-top shape. 

There’s also a potential for under gravel filters to develop dead spots as well, but with regular care and maintenance, this associated risk is greatly reduced. Plus, under gravel filters help minimize anaerobic decay processes since the water flowing around debris is fully oxygenated. For this reason, these filters have always been a topic pick for freshwater aquarium users. 

Some under gravel filters are also equipped with a reverse flow feature. These UGF filters also backflush the area underneath the filter plate which makes it easier to maintain your UGF and depend on it for long term use. 

Why are People Concerned About Under Gravel Filters?

If under gravel filters have been used as aquarium filtration solutions for years, why are people so divided about their safety? Unfortunately, just like any other tank filter, an under gravel filter can come with some drawbacks. 

While these classic filters still have their place in some tanks, modernized filters may be better equipped at handling the job depending on your aquarium’s needs. Some aquarists agree that under gravel filters are best suited for smaller freshwater tanks under 50 gallons large. 

Since the filters are so discreet, it’s easy to neglect their needed regular maintenance. However, taking care of your under gravel filter on a regular basis is key to its success. If you have a small tank, require an affordable option, and are committed to regular maintenance as needed, an under gravel filter may make a great, efficient filter option for your tanks. 

When Should You Not Use An Undergravel Filter?

Even if they have been used for years, undergravel filters can still be a good filtration option depending on your aquarium’s needs. However, when should you not use an undergravel filter? Here are a couple of scenarios in which you might want to invest in a different filter type: 

  • You’re Not Ready For Frequent Maintenance:

While every aquarium requires regular maintenance, you’ll probably need to budget in a little extra time if you choose an undergravel filter. These filters need to be thoroughly cleaned in order to function properly. Moreover, you’ll also want to make sure that vacuuming the gravel is a priority. 

  • Have A Larger Tank:

While under gravel filters are great because they provide a large surface area of filtration, they may not be able to properly filter large tanks on their own. This is because these filters are not designed to handle particularly large volumes of water. 

  • Need For Chemical Filtration: 

Under gravel filters perform a version of biological filtration which every tank needs. However, if you have the need for chemical filtration, an undergravel filter on its own simply is not going to cut it. 

  • You Have Rooted Aquatic Plants:

Under gravel filters can make it difficult for rooted plants to grow and situated themselves within the tank. 

Do All Filters Have These Drawbacks? 

It should be noted that all aquarium filters have some sort of drawback, even if it’s as trivial as price range. Whenever you switch to a new filter, you’ll want to monitor your tank and fish closely. 

Also, make sure you don’t rapidly switch up other aspects of your aquarium during this transition period. This way, you can make sure that any changes to your aquarium are a direct result of your filter. 

If you start to experience unreasonably clouded water, changes in aquatic plants or fish, your current filter may not be the best pick for your tank’s needs. This should be your default routine even when using a filter that isn’t an under gravel filter. 

endler tetra

How To Make Sure Your UGF Runs Properly

If you do choose to go with an under gravel filter, there are a couple things to keep in mind to make sure that it runs properly. 

  • Consider Adding In An Airstone

Air Stones are great additions to any tank and make it easier for air to be properly diffused throughout the entirety of the aquarium. 

  • Think About Your Substrate

Good UGF compatible substrates are pebble or stone substrates. It may be easier for debris to flow through these types of substrates, making it easier for your UGF to run properly.

Whatever media you use, it can’t be small enough to fall through the filter itself, or the quality of the water will suffer. You’ll probably be looking at a substrate layer that’s about 2-inches thick. 

  • Think About Your Fish

Make sure that your filter provides needed filtration for your tank inhabitants. Some fish that do well with under gravel filter setups include betta fish or even some types of shrimp

  • Invest In A Gravel Vacuum

You’ll want to invest in a high-quality gravel vacuum if you choose to get a UGF. Under gravel filters rely upon the cleanliness of the gravel to function properly, so it’s imperative that you make this practice a central part of your maintenance routine. 

  • Check For Dead Spots

Under Gravel Filters are vulnerable to developing harmful dead spots. Therefore, you’ll want to keep a close eye on your UGF to make sure that it’s staying fully efficient.  

  • Get A Suitable Air Pump

Your air pump must be strong and compatible with your water volume in order to work well with your under gravel filter. 

  • Consider Getting A Pre-filter

Oftentimes, under gravel filters aren’t used as a sole method of filtration. You can use a canister filter to remove any debris that might be floating in the water. This can greatly cut down on the amount of organic matter that’s passed through your UGF, making it more efficient and easier to maintain in general. 

  • Look For A UGF With Reverse Flow Options

If at all possible, it’s always better to have an under gravel filter that has the option to use a reverse flow feature since occasionally using this feature will make it easier to break up the debris as a whole. 

goldfish fish

Under Gravel Filters Still Work Well For Some Tanks

While under gravel filters aren’t always sufficient for all tanks on their own, they’re still an affordable filtration solution. Though these filters have been around for a long time, it doesn’t necessarily mean that they no longer work well. 

That being said, modernized filters like power filters or so forth are probably a better long-term investment, as modern filters are better suited to manage and balance water throughout the tank, not just whenever debris makes its way to the substrate. 

Under gravel filters can also be a great supplement to any tank, as their ability to cover a large amount of substrate surface area, unlike other filter types. Overall, an under gravel filter can still be effective when used and maintained properly. 

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