Our new ( 3 months) pond is about the same size you are planning, also in full sun most of the day. We have a skimmer with a Laguna pump (4200 gph) inside, which pumps water to our biological filter and waterfall about 25 feet away. It works really well. Our water stays clean and clear despite having very little plant coverage, plus leaves blowing in from our huge sycamore tree, which is about 40 ft. from the pond. No bottom drain so we do get some leaves on the pond bottom, but they are easy to scoop out. We only have 3 koi (8-10 in.) and one goldie at this time, so a really low fish load for the size of our pond.
We used the same skimmer in our smaller pond (1500 gal) with a smaller pump, 2000 gph ( I think it was Tetra) . It was in mostly shade except noon to four. The water was always clear and clean in that pond, as well, with no plant coverage. Same fish, too.
We do have to rinse the filter pad in the skimmer every few days lately, as the temps have warmed up finally. But we usually only rinse the pad once or twice a week. No algae to speak of on the falls but a nice coating on the pond floor and walls. The fishies love it! Very low maintenance, which
I love.