Do I need a pump for a pond?
I am using it to grow lotuses, but I also want to add a few goldfish to it to make it more interesting. Would I need to buy a pump for the fish, or would the plants provide the oxygen needed?
You don't need a pump for your pond. If you add goldfish, you must add submerged vegetation for them to eat, but never feed them anything else or the water will get foul. The submerged vegetation (anacharis, hornwort, cabomba) will add enough O2 for the fish.
Add a few mosquito fish to keep mosquitoes away.