[Chad]

For a fish only tank a canister or HOB filter would work just fine. But they produce nitrates so if you plan on having corals at all they aren't recommended.

For a reef tank most of us use what's called the Berlin method. You can read about that here http://en.wikipedia.org/wiki/Berlin_Method.

To that I add a nice skimmer and growing some chaetomorpha algae in the sump.

So for me rock, skimmer, cheato, are my filter.

 

[Chad]

...he said corals require clean water and HOB filter wont do it....

A canister won't either.

Canisters create nitrates but can't get rid of them. Corals don't like nitrates. So to really keep corals you need a way of getting rid of the nitrates, which is live rock. A canister simply can't (no matter how good it is) get rid of them but actually creates them.

 

[Chad]

Dry rock will eventually turn into live.
Though you do miss out on some of the fun things that come with live rock, like sponges, worms, tunicates, etc.

 

[Chad]

The filter doesn't trap nitrates. It creates them. Of more specifically the bacteria in the filter does. The bacteria in live rock can take that nitrate and convert it to nitrogen gas which leaves the tank entirely. So live rock removes nitrates but a canister just creates them.

So yes, you can do water changes but the filter will just create more. We always have to do water changes of course for various reasons, but why do more work than you have to?

 

[Chad]

I am suggesting using live rock as your filtration if you plan on having corals. If you don't, then the canister is just fine. Fish can handle low level nitrates.