cyano

[TheReefGeek]

I would investigate a brand-name skimmer to use, or at least find out the exact specs of the skimmer this guy is building for you.

Recirculating just means that one of the pumps is taking its feed water from the skimmer body, not from the sump.

Skimmers that come with sumps are notoriously weak, but if this is custom it might be fine. Just find out what style of skimmer it is, the pumps being used, etc.