We have to channel
@poconojoe as I sense this is going to need HIS enthusiasm, but here goes; the kind of algae you're probably referring to, which you don't want, is the free floating, single cell variety which blooms when the water conditions are right. Right as in too much decaying biomatter for whatever biofiltration you have, to handle. The UV light WILL kill this type but it'll also kill other good things in your pond. Here, in the hallowed halls of GPF (help me out here, PJ), we've found great success that is almost maintenance free, by using bog filtration (actually called; upflow wetland filtration, but we're lazy asses and just say 'bog').
This is the idea; all the algae coating your underwater surfaces is good algae; you want this. The fish nibble and the algae helps the water column. The free floating type needs to be out competed by other plants, hence your question. The answer is basically 'any plants', including other forms of algae but we like to make this a process and tie up all loose ends. A bog does this. What you need to keep the water clear of nutrients for the algae is plants in your bog, which sit above a pea gravel base, where you force water under and up. There are no pads to clean, there is no bioballs/shreds (that's what the pea gravel does and a lot better because there's a lot more of it), and no UV necessary.
Such as water lilies are NOT great for outcompeting the free-floating algae, but the blooms are nice! Most marginals sit at the sides and DO help, but you need a lot of them. Floating plants like water hyacinth and water lettuce are great at helping, but you will need to watch for your fish nibbling at roots and if they do, put them in protective floating baskets so they can still do their job.
Easy answer? Any plants IN your pond. Better answer? A bog filter where you have lots of plants AND more surface area for your good bacteria.
Btw, with winter, the fish are going to slow and you won't need anything as the bacteria will die (mostly) and start up again in the spring. THAT'S when you move in floaters and consider bog filtration to fix a lot of problems.
Hope I left something for PJ to comment on...I get so carried away when he's absent...
