Fish Tank Filter Installation: HOB, Canister, Sponge, Under Gravel

In Aquarium Filtersby PaulK

Does this sound familiar?

You get a new filter for your fish tank and you’re not sure how to install it or even where to put it.

If you’re a little confused about how to install your fish tank filter, then this short guide is for you.

Installing a Power/HOB Filter

Cartridges: Typically these type of filters come with cartridges for mechanical and chemical filtration. Some units have a sponge cartridge for biological filtration as well, but it’s better to use a ceramic media or lava rock for this purpose because they have tons more surface area for bacteria growth. Generally, it will be some sort of floss for the mechanical filter and carbon for the chemical filter. Some brands combine the two.

Each brand of HOB filter is different. You want to make sure that the coarse part of the mechanical filter is the first one the water goes through otherwise it will clog pretty rapidly. The hang on the back filter cartridges works fine for smaller tanks that aren’t overly stocked with messy fish. If you have a larger tank with tons of fish, you may want to upgrade to a canister filter.

Where to place a Power/HOB filter

A power hang-on-the-back filter will go on the back of the tank and you hang it on the back as close to the center as possible. If you hang it on one side or the other, it will have a hard time filtering all of the tank water. You’ll also want to place it as close to the heater as possible to get keep water temperature consistent throughout the tank. You put the intake tube side into the water and the chamber portion hangs on the back outside of the tank. The intake tube should hang about halfway down the inside of the tank. If it’s too long, you can either forgo the extension or cut it down in size with a hack saw.

Priming the Filter

To prime the filter, you will need to fill the chamber with water before plugging it in and turning it on.

Watch this video for Aquaclear setup and installation.

Watch this video for Marineland Penguin setup and installation.

Watch this video for Fluval setup and installation.

Marineland vs Aquaclear vs Fluval: Which is the best power filter?

Setting up a Canister Filter

Where to place a Canister Filter

Canister filters are placed underneath the tank to take advantage of gravity. The intake and output tubes are then placed on opposite ends of the tank. That creates good water flow. Getting good water circulation throughout the tank is important so that you don’t have any ‘dead spots’ where waste can build up. Canister filters do a much better job with this which is why they are the preferred filter for larger tanks. I have an article on Power Filters vs Canister Filters here.

Watch this video on Canister filter tube placement.

Canister filters come with several trays for media. The first tray that the water goes through should contain your mechanical filtration. Preferably, a coarse filter followed by a medium and lastly a fine denser filter. The second tray should contain your biological filter media. You may be able to fit this media in the third tray as well. The last tray would contain purifying media like carbon or Purigen. Something of that nature.


Filters that are submerged in the tank itself should be located by the water heater to circulate the heated water.

Aquaneat 3 PCS Aquarium Bio Sponge Filter Breeding Fry Betta Shrimp Nano Fish Tank 10 Gal

Aquaneat Bio Sponge Filter. Click photo for pricing info.

Sponge Filters

These filters are rather large cylindrical sponges that are attached to a tube and submerged in the tank. A pump is located outside the tank and is hooked up to the filter with a plastic tube. Since the sponge is rather large, it can be difficult to hide in the tank. Place the filter behind some plants, but make sure the filter can suck the water in.

Sponge filters are the easiest to set up and maintain. You just slip the sponge on the plastic shaft and connect the bottom piece, then thread the smaller air tube through the main tube and attach it to the protruding hole so it fits tightly. Then attach the main tube to the top. You’re done.

Under Gravel Filters

Penn Plax Undergravel Filter – Premium Aquarium 4 Filter Plate System Designed to Fit 40/50 Gallon Tanks

Penn Plax Undergravel Filter. Click photo for pricing info.

As the name implies these filters will be installed at the bottom of the tank under the substrate. The filter must go in first before the substrate. Then the substrate (gravel) is placed on top. The water gets sucked through the gravel which filters the waste. The substrate must be vacuumed regularly to get rid of the waste products.

Corner Filters

The corner filter is like the sponge filter, but fits neatly in the back corner of the tank and can be easily hidden. They are good for smaller tanks only.

Here is a decent forum post on Fish Lore about the subject.

When it comes to fishkeeping, what is your single biggest challenge or frustration? Leave a comment below.

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