Does a pond really need direct sun?

Question

I'm considering putting in a pond on the shady south (non-equator-facing) of my single-story house. Various advice that I have seen online says that a pond needs at least half a day of full sun, and if it has fish, then full sun.

However, the house that I grew up in also had a pond in this position - hard up against the south wall of the two-storey house. It had goldfish, and a little bit of pondweed, and some algae. It was my job to clean the filter. I can't remember any problems that the shady spot caused. The fish seemed to be fine, and didn't get sick often that I remember.

So, what is behind this advice? Why would a pond need direct sunlight?

Answer 1

I have a pond that faces south but the nearby tree has grown through the years and it is now in some shade.

The water lilies do not flower but the iris and pickerel weed do. The fish don't seem to care.

Sunlight powers flowering so it depends on what plants you have and the nitrogen load on the system. Not enough light and algae will proliferate faster than plants.

Make sure you have a pump that pumps all the water in the pond at least once an hour, more is better.

Plant some disposable plants that tolerate lower light like Mimulus guttatus (Yellow Monkey Flower) and grow fast to soak up the nitrogen and reduce the amount available for algae.

Answer 2

Yes and no, depends on where you are and what is in the pond, and depth. A 2ft deep pond in the south (eg. TX) can get too hot for any fish except air breathers like paradise. If you want to bloom water lilies the book says you need sun ,but I get regular blooms with only 3 hours of morning sun. Louisiana Iris bloom well ( early spring) in the same location (bog/filter). I think full sun should be avoided because of heating, especially for gold fish. However, if relatively deep (5 ft) the temperature should be satisfactory. Bright sky ( no trees directly overhead) seems enough light for most water plants and is what I would recommend.