I have 17" of clearance from top of tank and 6" from top of skimmer. This is one of two sumps, one is 90 and the other is 70, and the main tank is a 240, so I have a a fair amount of volume. I'm already ready for a bigger tank...
I hate placing my reactors in the sump, but it's better than it leaking. I only run soft tubing ATM, so it's just piece of mind. But to echo what another person mentioned, it's a PITA to check on media movement.
