Look into a herbie drain setup, also known as a full siphon drain. Requires 3 holes drilled; main drain, backup drain, and return.
I'm a big fan of all-in-one tanks. I have a 28g nanocube drilled with a sump
If you're going to setup a 50g tank, you may as well setup a real sized sump. 20-30 gallons with a refugium section.