HOB filters *insert drum roll here* literally hang on the back of a tank. They are somewhere inbetween canister and internal filters. They offer good bang for buck and are definitely a step up from internal filters as they introduce seperate biological filtration but not on the powerhouse level a canister filter does.

The two important points of HOB’s are:

  1. They offer separate biological and mechanical filtration
  2. They don’t take any room up inside the tank

The advantage of separate biological filtration means your bacteria aren’t disturbed and you can use proper biological media to maximise your bacteria in the space you have. The sponges used in internal filters are less efficient than dedicated bio media found in HOB filters.

The placing of the filter itself can be both an aesthetic and practical positive. A big black box in your tank might annoy you (it sure annoys me) but with a HOB filter all you have to see is a pipe with a strainer on it along the back wall, which can easily be masked by clever plant/ornament placement.

HOB filter with biolwheel

Example of HOB filter with biowheel

There are HOB filters on the market with “Bio-wheels”. The theory being that water makes the wheel spin and the bacteria get a boost of oxygen because the wheel isn’t completely submerged as it spins and there’s a lot more oxygen in air then there is in water. I’ve read bio-wheels are prone to clogging (stop spinning) and are often removed altogether and just replaced with bio media so be cautious.

Noise too can be an issue as the returns on HOB filters usually ‘dump’ the water back into the tank to oxygenate it which creates a trickle noise. If you’ve ever seen one of those indoor fountains you know what I’m talking about.

Ironically enough trickling water is supposed to make you relaxed. If you’re a normal human being however the noise will simply drive you nuts and make you want to go to the toilet more often. This is especially annoying in the middle of the night when everything is quieter except that god almighty water noise coming from your fish tank.

Fortunately there are cheap DIY options out there and some filters even come with extender kits to get rid of the noise. Basically the larger the gap between your tank water level and the outtake of the filter, the noisier it will be so when choosing a HOB filter take this into consideration.

Aquaclear 30

Aquaclear 30

As far as which HOB filter to get, I’ve heard very good things about Hagen’s AquaClear series. They offer plenty of room for media and you can decide exactly how much mechanical vs. biological filtration you want to customise depending on your individual tank.

Keep in mind that the larger models do require space behind the tank. If you’re like me and have the tank on a stand next to a back wall and don’t want to bring it forward, a HOB filter might not be the best choice for you.

These filters start at about $20′ish and work there way up to just over $100.


Pros:

  • A good HOB filter is a lot cheaper then a good canister filter

  • Don’t take up any space inside tank

  • Separate biological filtration

  • Ability to be customised between mechanical and biological filtration to suit your tank

  • Do a better jon on larger tanks then internal filters

  • Easy to clean as everything is outside the tank



Cons:

  • Water return can be noisy

  • Require adequate space behind a tank



Related posts that might interest you:
  1. Filtering a Goldfish Tank: Canister Filters
  2. Filtering a Goldfish Tank: Internal Filters
  3. Filtering a Goldfish Tank: Undergravel Filters
  4. Which filter media to use for your goldfish tank?
  5. Choosing a filter for your Goldfish Aquarium