A lot of saltwater tanks have sumps or all in one systems for filtration, but a lot of hobbyists also use HOB or canister filters especially if they are new to the hobby or want to save a couple bucks. I prefer HOB personally as they are easier to clean, take up less space, and less prone to leaks. Canister filters can hold more media, and cause less salt spray, but they are more annoying in my opinion to take apart and clean. What is you're preferred method if you had to choose.
