Ang;3888494; said:sump
overflows to a lower tank on the bottom filled with bio-balls etc. (you can look up sumps for diagrams/explanations)
For tanks that size, sumps are the best way to go.
Ang;3888557; said:1/3 volume of tank for heavy bio-load
1/4 for normal load
So it kinda depends on your stock. But its always good to go bigger. That way if you change your stock later on, you wont be underfiltered.
Ang;3888572; said:here
http://www.oscarfishlover.com/the-sump-filter
this guy has a 300 gallon. showing his sump setup