Sump overflow box

[surfnturf]

I am upgrading to a 55 gal and want to use my 20 for a sump. I am looking at overflow boxes since the tank I have is not drilled. What kind of flow rate do I need to look at. There is an eshopps pf nano overflow box I was looking at online rated at 200 gph. Will this be enough? Can I use my eheim 2213 for the return? Or do I need a sump pump?

Thanks,


Surfnturf

5 discus
1 german blue ram
9 harlequin rasboras
5 corydoras
20 long
Eheim 2213
Finnex planted plus