dumb ? what's a close system?

[nashorn]

O.K. this is new to me. So I had to ask:confused:

[popimp06]

a closed loop is when you have a direct input and output on a pump one that is not going through a sump filter skimmer ect

[REMF]

Not dumb, if you meant closed loop, here is a good place to find cool things Melevsreef is a awesome tool. Click HERE (http://www.melevsreef.com/closedloop.html) to see and read about a closed loop.