519 gallon tank.
8x 1.5" bulkheads that feed into 4x 2" pipes. The 4x 2" pipes run into a 65 gallon mechanical sump with 4x 7" filter socks and 3 layers of filtering pad/sponge/floss. The 65 gallon mechanical sump feeds into a 65 gallon pump-house sump via 2x 4" bulkheads. The pump-house sump has 2x Quiet one 14000s that return back to the tank via 2x 1.5" return lines. There will also be a mag 12 in the sump that runs to a 27 gallon bio sump that has 15 gallons of 1" bio-balls in it. The bio-sump feeds back into the mechanical sump.I am going with the bio sump and a 2GPH continuous water change system.
The sumps will maintain a 40-50 percent water level and provide for spill over in case of a pump failure.
I was contemplating using 2x FBF filters, and a 12x 22" DIY coil denitrators, but that may be a future upgrade.