I'll try my best Ben.
120 gallon agressive tank with 37 gallon sump will work, but it all depends on a couple things.
1) Return pump - when it fails or at power outage, your tank water will begin to siphon back into the sump. The return location in the tank must be positioned high enough in the tank to not allow more water to siphon back and exceed your sump capacity.
Some folks will drill a small hole in the return ( spray bar or whatever using ) an inch or so below normal operating level, to allow this siphon to break )
2) When pump fails or at power outage the water in both overflows will also drain down to the sump, until the tank water level reaches the bottom of the slots on each overflow.
3) Say you normally run your sump at 50% full - that is about 18.5 gallons based upon your using the 37 gallon tank - and as long as the volume of water draining back to your tank from the return line and overflows does not exceed the remaining 18.5 gallon capacity of the sump - then you'll be good to go.
It all depends on how far down the overflows are located, depth of the slots in each overflow, and the where the siphon breaks on the return line.
Stuff to put in the sump - lots of choices.
Protein skimmer, heater or heaters, drip plate for carbon bags, wet/dry if going that route, place to add your additives and do water changes, partitions for sand beds or refugiums ... etc.. the list goes on.
Hard to give you a definitive answer but these are things to consider for sure.
Otherwise - sump overflow - wet floor - upset hobbiest
HTH Brian
[ June 01, 2001: Message edited by: broomer5 ]
