I've been thinking about getting my feet wet with clownfish for over a year. I've got plenty of experience with freshwater tanks. I probably won't actually do anything about getting a saltwater tank for a few more years. It wouldn't be anything big, just a 20g or so. It'd only have clownfish, marine fish get pretty big, and most of them are wild caught. If I do get clownfish, I'd convert one of the tanks I've already got. How do marine tanks differ from freshwater? Do clownfish need need sand, or would they be okay with gravel? What about filtration? The best filters on my tanks so far are canister filters. I don't want to deal with a sump, none of my current tanks are drilled, and I'd have no clue how to maintain it.