Above it, with 500 litr/hr pump, wet/dry with foam and bioballs.
Inside the last chamber ( from where water is pumped back into the tank ) I have another pump (2500 litres/hour ) that sends part of the filtered water back to chamber 2 to do the sump circuit again.
Alongside the sump ( and working with the sump ) I have an Eheim cannister full of Chemi Pure ( could be full of carbon, if needed ),
and I still would like to have more, because this tank is FULL.
In all my other tanks, the least I have is 2 big cannisters ( 2280's and 2260' and 2250 Eheims as well as those overflow boxes ??)
Our 300 gallon tank system has a ProClear 400 Wet dry filter with a CA-6000 pump (1560 gph) for biological filtration; for mechanical filtration, two Rainbow Lifeguard spa filters run by a big Reef Flo Hammerhead pump (5800 gph). For redundant backup filtration we have an FX5 with a 40 Watt Pentair Aquatics UV sterilizer connected to it.
I've got a 10 gal tank set up at the moment with a diy overflow, buffer tank and sump with ~8 gal of filter media, the sump and buffer tank hold almost twice as much water volume as the 10 gal it's self
Wet Dry rated for 400 gallon tank doing 2200 gph (sump has 2 litres of bio-home 10 bags of nitra-zorb 1lb of carbon)
FX5
2 xp3's 1 mechanical 1 chemical hooked to a turbo twist 18 uv sterilizer
And im thinking of adding an xp4 or maybe another fx5 for when i go away to college.
(1) 10g BW tank w/ ~15lbs of live rock & 16lbs of fine white argonite sand, 35xturnover from a penguin 250 and ACmini and i just took out my little 60gph rio that i had hidden in the rocks. i'm still not satisfied with the water flow and soon i'm going to replace the ACmini w/ PS75 needlewheel skimmer @ 315gph. i love my water flow and my fish don't seem to mind