I actually built my first sump in the basement of my old house for a saltwater reef tank I used to run. With saltwater the extra water in a large sump (mine is a 300G Rubbermaid) help minimize changes in water chemistry. When I moved and built my house I set up the sump in the crawl-space. Now that I do freshwater-only, the sump isn't as necessary, but I still love the space the sumps affords for DIY filtration.
For my latest tank I decided to go closed-loop, mostly because I need it to be as silent as possible - it is in my 4th grade classroom.
Reeflo Blowhole 1100 powered NuClear canister setup (nowhere near as monstrous as most of the filtration in this thread):
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This pump is the quietest pump I have ever heard, as close to absolutely silent as a pump can be.
Nice..... Were you able to get the school to pay for the setup?

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