I thought you were talking about a pond of substantial volume. When there is lots of water, temps hold steady, but with tiny puddles of 100 gallons or less, the fluctuations can be drastic, especially if the water feature gets any sun.
I had a 55 gal tank in Milwaukee that would easily overheat when sun took it out of shadows (easily reaching 90'F), but when I used a 1500 gal pond as a sump, the temps held steady enough to keep fish.
Below is the tank, and with only a few hours of sun per day, became quite choked with algae.
below the tank, where water is pumped up from the pond below to the tank, to keep temps steady.
I had a 55 gal tank in Milwaukee that would easily overheat when sun took it out of shadows (easily reaching 90'F), but when I used a 1500 gal pond as a sump, the temps held steady enough to keep fish.
Below is the tank, and with only a few hours of sun per day, became quite choked with algae.
below the tank, where water is pumped up from the pond below to the tank, to keep temps steady.