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The Overhead Filter

filed under: Gear and Equipment

In some countries, overhead filters are some of the most popular aquairum filters. These are also one of the most efficient, and possibly the easiest to maintain commercial filters one can buy.

I first encounted this type of filter roughly 25 years ago. The hobby was very different back then. During that era, the final word in filteration comes down to a few words: undergravel filters. Undergravel filters were considered good for what they do, mainly because, at that time, the typical hobbyist don't usually have access to better types filtration systems.

When the first overhead filters hit the market, compared to anything out there, they were beasts! Prior to the overhead filter, a typical filtration system is powered by an air pump, with very low water flow rates. 

With the new pump-powered overhead filter, the fish keeper now enjoyed, not only higher flow rates but also a better alternative to the standard undergravel filter.

People now had new options on how to set up their tanks, such as keeping messy fish on a bare tank. This new type of filter did wonders to my costomized, side tinted, 60 gallon goldfish tank.

And thanks to its efficiency and ease of maintenance, fish not only stayed healthier and lived longer, but I am sure that keepers did as well.

Unlike the models today, which use powerheads, these older overhead filters welded noisy, motorized, exterior pumps, situated outside the tank. Other than the pump, nothing has changed much in the design since then. And nothing really had to.

Some of the first overhead filters use external pumps like these.

What, 25 years ago, was considered a high-tech piece of filtration system, we now acknowledge these overhead filters as quite simple. And while the overhead filter is now accepted to be very basic in today's standards, I still consider it as one of the most efficient filters you can buy.

These overhead filters are made of basically two things, a water pump (usually a submersible powerhead), and a filterbox.

A powerhead is placed inside the tank, under the water level. This pumps water above the tank, and into the filter box containing the media.

These boxs can contain virtually any filter media the fish keeper would wish to use.  Polyfilter, activated carbon, bio-balls, or a combination of the three are some of the more popular choices. Gravity does the rest as it draws down filtered water to an outlet going back into the tank.


As mentioned, these filters are simply boxes that can hold just about any media a fishkeeper can think of. Some of the more advanced systems have stackable filter boxes making for an efficient, multi-stage (and possibly  trickle) filtration. These stackable filters are some of the best filters one can own.

Efficiency and performance

Flowrate is where the overhead filter really beats most other types of filters, including canister filters. The simplicity of its design is also its greatest strength.

In an overhead filter, a pump pushes water up into the filterbox and lets gravity do the rest. This means that, unlike systems such as canister filters, water-flow is not forced through any filter media, which impedes flowrate ( and even stops it all together if the media  becomes badly clogs).


Another area where the overhead filter wins over many types of filters in is in the safety department. Because everything goes above the tank, there is little danger that a leak anywhere in the filtration system will drain the tank out. On the other hand, something like a leaking canister filter(or any of its two pipes) can quickly drain a tank overnight.

When I was a kid, overhead filters were not yet available, and we used used air pumps to power filters such as box filters and under gravel filters. These pumps pump air into an airline hose that is connected to a filter. The pumps are located outside the tank. 

One day, my family decided to take a weekend trip and when we returned, I discovered my 20 gallon aquarium drained to the gravel. All my fish where dead, including my favorite fish, a 3 year old oranda goldfish. Upon inspection, we discovered that one of the airline hoses was dislodged from the air pump. Water back-flowed into the airline tubing and siphoned the entire contents of the tank out.  All this touble cuased by an airline filter! Imagine how faster it would drain if, say, a canister filter leaks.

But if I had been using an overhead filter, the story would not have ended as tragic.


Other than the pump, everything is located outside the tank so cleaning, and replacing media can be as simple as lifting the filter box cover, replacing the old media, and putting the cover back again. All this can be done in seconds, In most cases, you do not even have to turn the pump off..


The simple design means that these filters can be acquired every cheaply. Some are just slightly more expensive than the pump that is included in the package. In terms of filtering performance per buck, these filters are probably king.


All the disadvantages I could think of goes towards aesthetics. Filters, even the most expensive ones, are generally unsightly. If you will use an overhead filter, your tank really needs to have a hood to cover it up, unless you don't mind seeing a big box sitting  on top of your aquarium every time you want to look at your fish.

Some overhead filters can get really ugly quick.

If you have the stackable type, a hood might not even be an option.

Another problem is the pump. Most systems use a submersible pump, and these will use some space in the tank. They can be quite unsightly if the can not be hidden behind some decor.