Water change question?

[sufunk]

I'm getting ready to do my 1st water change on my new 180g and have a question. I've done a million on my 36g but never on a big tank.

I'm planning on doing a 40 gallon change but when i'm siphoning out the water, do i leave the skimmer and return pumps on or turn them off? I'm assuming on but not sure?

The tank is a AGA 180 with dual overflows, 45g sump with a mag 12 return.

 

[asm481]

On my 125 with 40 basement sump I leave the skimmer running, but the return off. I empty my sump so return pump would run dry! I do leave my closed loop running through changes as it is all below center of tank meaning in and output are low in tank. If your setup is what I am thinking you will def want to shut off return pump as you will lower level and return will suck sump dry and burn up the pump.