There are many sides to canister filters in saltwater. Many people don't like them. That's not to say that they don't have their benefits in a saltwater tank. If I may ask a few questions about your set up and what you plan on keeping this will help determine the best way for you to use your canister filters in saltwater.

Are you planning on keeping a reef environment, a FOWLR tank (fish only with live rock), or swim tank (fish only with lace or dead rock)? These are the three basic tank set ups in saltwater.

With a reef tank a canister filter is best set up as only for water movement and to only place things like carbon in. They do have a place in saltwater because they can help the aquarist(?) maintain better water quaility and clearer water. However, especially in a reef tank, they have a tendancy to be bacteria magnets. This is why so many talk them down. Because they sit under the tank and are enclosed people tend to forget about them. Maintenance is never as important as when you have a canister filter.

If you use one on a FOWLR or swim tank then you can use your canister with a lot of other additions. I currently use two canisters on my 125 swim tank and I use carbon, the poly filters and some other stuff to help keep my stuff stable. Because of this I have to keep up on their maintance and keep them clean.

With a reef and FOWLR system there is honestly little need for a canister filter and they can create some headaches. The live rock is thought of as your filter and helps keep things balanced. In swim tanks this is harder to accomplish. There are other types of filters out there to do this (wet, dry and the such). Since you already have the canisters though you can put them to use for you. You just have to determine at which rate and be diligent!

I don't know if this clears up any confusion or makes it more difficult. I just don't think canisters are all evil and there can be positives found when used properly.

Angie