External Filter Vs Sump

New to the fish aquarium hobby and weighing your aquarium filter options? It can be a difficult decision, believe me. I have been at this for many years and have tried just about every filter out there for my fish tank. Recently, I noticed a lot of gunk building up at the bottom of my tank. My external filters have always been good to me, but I started weighing the options between an external filter Vs sump. Would one be better for me than the other? Let’s see what I discovered.

Comparisons between external filter Vs sump

External Filters sump
  • Affordable
  • easy to install
  • Make the tank messy
  • some can be noisy
  • May not keep surface clean
  • May cost more than an external filter
  • Installation may not be that easy for beginners
  • Hide media, filters and accessories.
  • relatively quiet
  • Keeps the surface clean


When it comes to filtration, there can be a lot of frustration. If you don’t have the correct size filter installed in your tank, you will have pretty bad filtration. You will start to notice cloudy water, dirt on the bottom of the tank, and potentially sick fish. It is important to know how well a sump and canister filter work in certain tanks.

canister filter

These filters draw water through a riser tube and into an external filter or container where it is then forced through various filter media to clean the dirty water. There are several options as to how the water will flow through the filter.

The media these filters provide are chemical, mechanical, and/or biological filtration. This all depends on which one you choose to use. Once the water has filtered through the container, it returns to the tank. Most external filter models have water pumps that are built into the cover or base, but some require a separate external pump.

Sump or Sump

A sump is not actually a filter, it just houses the filtration system of your choice. You must install a circulation pump inside the sump if it is submersible or plumb it adjacent to the sump if it is not submersible. You can buy sump setups or build your own.

Water is then pumped from the sump into the aquarium and then back into the sump. If you do it this way, the pump can run constantly. If no water is entering the sump, it will be necessary to cycle the pump on and off as the sump collects water. To me, this seems like a pain. You’d have to install a float switch, like you find on old school toilets, or switches that turn on automatically when the water starts to go down.

Most people use sumps with drip filters that allow water to flow through the filter tower and into the sump.

Be aware of your team

Before you go all out and just put a filter or sump in your tank, here are a few things to know about each.

Be aware of your external filter

If used correctly, canister filters are a great tool for your tank. A top filter gives you the advantage of being able to choose which filtration is ideal for your tank because you can customize the filter media.

Canister filters generally have a lower need for maintenance than power and sump filters because the water is forced through the media rather than flowing over or around the media. Most of these filters also return water to the tank through a spray bar. This reduces evaporation and draft.

With these, there is no need to install a box on the outside or inside of your tank. There are really no special requirements and they are easy to maintain.

Be aware of your sump system

Sumps may seem like a complex setup, but they provide your tank with adequate water flow and a place to store all the stuff that normally clutters the walls and bottom of your tank. On one side you can have a hanging filter, heater, thermometer, pipes, cables and more. With the sump box, you can add all the stuff to it, declutter your tank and give your fish more room to swim.

Sumps also keep surface water free of contaminants and keep water levels stable in the display tank. If you have a plumbing system (tubes and pipes coming out of your tank to carry water to filters and other necessary equipment), the sump is what collects the water. This prevents the water from overflowing, as noted above.


Here’s what you need to know about installing an external filter in front of a sump.

Installation of the external filter

The first thing to do is install the inlet and outlet flow pipes. Be sure to place them exactly where you want them because the installation is permanent. You will then need to place the canister where it will be running at all times and measure the length between the pipes and the corresponding ports on the filter.

It is necessary to cut the hose so that the inlet pipe goes to the inlet port of the container and the outlet of the container connects the outlet pipe to the tank.

You then need to fill the basket containing the filter with the recommended media or you can choose your own based on the filter guidelines. Make sure you place the basket in the correct way in the container and that the inlet and outlet pipes match.

You will then need to submerge the large o-ring in the water to wet it and then place it on top of the canister in the groove (this varies by filter model). Turn on the power and check for leaks. If there is a leak, reset the O-ring; if not, you’re good to go.

sump installation

If you choose to make your own sump, there are several ways to build and install. I am going to take the easy route and tell you how to install a ProFlex pre-built sump.

For this sump, you need to remove a few screws, attach the bottom tray from the biofilter kit (sold separately), slide the adjustable wall to the top, and hold it in place with one hand. You will then need to fill the space above the bottom tray in the second chamber with the biological media from the kit.

Then place the filter kit dip pan on the second row of tabs in chamber two, slide the adjustable wall down so the spout rests on the dip pan, and position the sump in the desired position under the aquarium.

Finally, connect the submersible return pump inside the third chamber and connect the return tube to the outlet of the pump.


In my honest opinion, I think an external filter is an ideal choice for regular fish tanks, that is, if you don’t mind a bit of a mess in your tank. Sure, the sump is perfect for hiding all your media and accessories, but it doesn’t act as a filter unless you buy one separately. The external filter filters the water without the need for additional parts or frustrating installation. After weighing these options, I decided to stick with the canister filter setup and simply try a different brand. If you have any comments, concerns, or questions, feel free to send us a message!

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