Do UV bulbs really help against algae infestation; what if the pond gets a lot of sunlight?
Yes, however only against suspended algae that makes the water murky; they do not help against string algae. Concerning sunlight, the OASE dealer has information materials available on this topic.
A UV bulb by itself is only of little help as it only flocculates the algae. There must be a filter downstream from the UV bulb that filters out these clumps of algae. You will find the suitable filter in the OASE product offerings.