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External Filter vs Internal Filter vs Hang on Back Filter

Updated on March 10, 2010

So you're setting up a fish tank, or maybe you already have one and you would like to upgrade your filter. But what filter should you choose?

As someone who owns all three types of filter, I'm in a fairly good position to give you advice, and let me cut to the chase before I proceed with the analysis of all filter options, if you want a quiet filter with excellent filtration, it's pretty much well impossible to go past Eheim external cannister filters. They're my preferred option, especially for tanks with messy fish in them like cichlids.

Still, let's explore all the options.

Hang on Back Filters

Hang on back filters hang on the back of your aquarium. AquaClear HOB's are the industry recommended HOB filters and if you are going to go the hang on back way, I suggest you make the investment in an Aqua Clear. As you'll already know (or soon learn if you are a newbie,) equipment makes all the difference, and if you cheap out on it, trust me, you will be upgrading for months and years to come. Spend as much as you can afford on filters, they are essential to the running of your aquarium and the health of your fish.

HOB's, if well made, can be quiet. If not, they can be rattly, loud things and if they break, they can siphon your tank as far down as the uptake pipe goes, which can be a real worry.

Internal Filters

These were the filters I started off with and they are filters I'd now not recommend at all. Their attraction is that they are cheap, but most cheap internal filters are fairly noisy, don't work all that well, and can suck little fish against their vents. I'm in the process of swapping all my internal filters out for external canisters. The only thing they are quite good for is adding additional water movement to the tank, but you don't need a filter for that, just a power head.

External Canister Filters

Buy a good external canister filter and you won't have to replace it for years. As I mentioned up above, my personal favorites are Eheims because they have a reputation for quality, run whisper quiet and are very easy to dissemble and clean. The more recent models come with filter media replacements, which is most excellent. A good Eheim only needs to be cleaned out once every six months or so, which compares very favorably to the HOB option.


For any tank 20 gallons on more, I recommend an external canister from Eheim. For smaller tanks, a nice Aqua Clear HOB filter will serve you well.


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      bikeman 6 years ago

      I use a hang on back filter on my small aquarium but have often wondered if it was actually effective as internal filters are much more widely sold.

      Also it is a concern that as the filter clogs water tends to flow over it rather than through it so efficiency decreases. Secondly the filters are usually slotted in so you have to buy the correct filter rather than just popping a bit of cut foam like you can with an internal filter.

      One think I don't agree with you is you state that a HOB filter can syphon the aquarium in the event of a fault. This is not ture since the design of a HOB filter precludes syphoning of the aquarium since the waterfall is always lower than the body of the unit so it can't overflow.