Canister filters.
 

Just wondering what everybody thought of canister filters and if anyone is using them on their reef

Not too many use canisters in salt water at all, if you still want to utilize your canister filter in a reef you must get rid of sponges, use only for activated carbon and phosphate nitrite etc, removal media.
The reason is that sponges will accumulate waste very quickly and will start decaying process, that will pollute your tank and Po4 an No3 will shoot through the roof.

As he ^ said. Although you can also put live rock rubble in the canister. Really it is not very useful in a reef tank at all, more of a pain in the butt to clean than anything.

i pack an xp1 full of carbon and gfo. found it to be a better option that most commerically made carbon/phosphate reactors.