Filtering a Goldfish Tank or Aquarium: Canister Filters
A canister filter is without a doubt the best type of filtration for a goldfish tank. A canister filter is essentially a hose fed “box” that houses copious amount of mechanical and biological filtration with the choice of exactly how you want to filter your tank. Because of their design and the fact they are completely external to the tank the area inside the canister filters allows for the largest amount of filtration to take place.
So what’s the catch?
Canister filters are hugely expensive compared to HOB or internal filters.
With Fluval’s ’05 series carrying a six year warranty and the sheer ease of use, i’d say that extra cost was more then worth it. With a canister filter you have two hoses inside the tank, an intake and an output and conventially you have them on either side along the back wall. Parts of the better brands are also readily available so theoretically you can keep one of these going for years.
Fluval 205 internal parts
Like the HOB filter mechanical and biological filtration are separate and the biggest advantage being the sheer amount of media you can store in the canister. It’s not uncommon to fit two or three times as much media in a canister filter as you would fit into a HOB filter rated for the same size tank.
With the canister filter also comes the introduction of priming. Canister filters sit below the tank so while the output is pump fed, the intake is gravity fed and initially there is no suction to get this going. The good filters will have a system in place ranging from a hand driven pump to completely automated systems while the cheaper options leave you with a hose and the risk of a mouthful of tank water everytime you need to start it up.
Under normal use you won’t be cleaning a canister filter too often, I clean mine every 2 months or so and I’ve yet to see the pads super gunked up beyond some muck at the bottom.
With the Fluval ’05′s you simply flip a lever up, disconnect the hoses, carry the canister to a basin, unclip the unit, pull out the mechanical media (sponge tray) swoosh it around in a bucket of old tank water, empty the gunk water out of the canister and then put it back together again.
The lever on the hose ensures that syphon gravity is held so when you reconnect it and flip the lever down the filter will auto feed back into the canister so no priming is required. On occasion after turning the power back on after a clean I have had to manually pump the unit two or three times to get it going but that’s no big deal.
On the otherhand If you don’t mind a bit of work pulling apart the filter and then starting it up again after cleaning, the cheaper options might suit you.
One other consideration to take into account is “bypass”. Bypass happens when, due to bad design of the filter or too long between cleanings, water is able to bypass mechanical and biological media you have in place and simply return to the tank via the output.
It doesn’t take much for this to happen in cheaper canister filters. Usually badly designed internal components or an incorrectly sized sponge is all it takes for them to stop running at maximum filtration efficiency.
Personally i’d stick with Fluvals but if you’ve got the extra money definitely take a look at the Eheim’s as they are built a bit better and are slightly more efficient but they cost a fair bit more too.
Pros
- The most efficient type of filtration available
- Huge amount of media able to be stored in the canister
- Maximum water flow through the tank
- Due to increase in size of filter media, cleaning of the filter isn’t required as often
- Good canister filters are dead easy to clean
Cons:
- Very steep upfront cost, often more then the tank itself
- Cheaper models prone to suffer from “bypass”
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