Skimmer for small sump?

[banghair]

As in my last post, still feeling a little lost.

I have a 40g display and a 20g long sump. It seems like only a nano skimmer will fit in my sump, but I’m reading that it’s not worth it to get a nano skimmer? And would it to what it has to for a 40g display? Should
I look into alternatives? If so what kind? Please help me out! So close to finishing this tank and finally getting it going.

 

[FUNGI]

If you have room in the back, get a HOB and run the water input at the highest water level part of your sump