Plant suggestions for low-light outdoor pond

[GobyMaster11276]

Title says most of it. I have a 300l goldfish pond, lightly stocked (3 fish) and under shade most of the time. The water is quite cold due to its outdoor setting and lack of heating, so I need plants that will withstand and thrive in these conditions. What species would work?

 

[Circus]

Common Hornwort, also often called Coonstail, works well for ponds. Well enough you will likely have to thin it out regularly. It does well in lowlights and cold water. Most of the hornwort in my tanks was raised in ponds. Can be anchored to the bottom or left floating, it doesn't actually have roots but absorbs nutrients through the stem.
Scientific name: Ceratophyllum demersum.

 

[GobyMaster11276]

Common Hornwort, also often called Coonstail, works well for ponds. Well enough you will likely have to thin it out regularly. It does well in lowlights and cold water. Most of the hornwort in my tanks was raised in ponds. Can be anchored to the bottom or left floating, it doesn't actually have roots but absorbs nutrients through the stem.
Scientific name: Ceratophyllum demersum.

I’ll keep an eye out for it! From your knowledge, is it very expensive?

 

[Circus]

I’ll keep an eye out for it! From your knowledge, is it very expensive?

Not at all for small bunches, I am not sure about bulk. I just paid 3.99 for bunch about a foot long, with 6 separate plants at the fish store. You might ask your LFS if you can get a bulk deal. Or you can try emailing one of the online retailers to see if they would be willing to cut you a deal if you want a lot of it. I have also seen it for sale by private owners on different online market places, like Facebook or craigslist.