I m running 2 skimmer too. A 400L NW skimmer + a 500L venturi. I notice that even w both skimmer, my older NW is still skimming.
I have also seen for myself that 2 reefer who was initially running a 800L NW skimmer, after putting in another 400L NW skimmer, both are still skimming too.
Since u are not running power hungry skimmer, why not just leave it there. The most is it will consume $5-$10/month nia, which is affordable.