09-29-2008, 11:16 PM
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That's not a canister filter, that's usually referred to as an internal power filter. I don't use any myself, as the only one I have came in a big lot of aquarium stuff and doesn't work.
Personally, the only time I'd use one of them instead of a standard hang-on-back power filter is if the tank was positioned such as to restrict having anything hanging off of it. Regular HOB filters give you more freedom when it comes to using customized filter media, plus they generally have a large open space where you can toss in media bags with any sort of filter media such as carbon, ceramic rings, filter floss, peat, etc etc.
However, if you've already got the filter running on the tank, I strongly advise against replacing it altogether. Replacing a filter will almost assuredly lead to at least a mini-cycle. If you want to switch, I would add the new filter, let it run on the tank for a month or so, then remove the old one. Or, you could just run both for extra filtration.