Thanks for the kind words!
I ended up taking down these ponds, mainly because they became a lot of maintenance work and I had less time to enjoy them than before. As the weather gets colder, sure I'm set up for the fish to be fine in Southern California, but that doesn't mean I want to hang out there all that much. Something to think about, even for the warmer climates!
So I distributed my fish among my tanks and am now only running the daphnia culture, which is still thriving quite well!
So let's do a post-mortem...
What worked well?
Heaters, man. The 200 watt heater in the 15 gallons of water kept the fish nice and toasty even on the coldest mornings. I think this stability encouraged breeding. There were babies showing up in every tub!
On the same note, feeding fry food every night, regardless of whether I saw fry or not, probably helped as well.
The lights were great. I would NOT do a pond without a light, because I want a better view!
What would I do differently?
The box filter was a bad idea. In practice, it's just too much maintenance. Quite honestly, I should have just used sponge filters, or better yet, probably nothing with just an airstone. I think I would have even started to play with HOB filters, adapting them to the weather and angled sides of the tubs.
Duckweed was a bad idea. It got everywhere, whether I wanted it or not. I liked the frogbit.
I would have started with more plants up front. I should have put in a LOT more guppy grass at the outset, to prevent the algae from taking hold. Alternatively, I could have planted a lot of water sprite, but I think the floating plants were most conducive to breeding and protecting the fry.
I would have used finer gravel. The cheap pea gravel is just not very attractive.
I would have made the "electrical boxes" easier to service. The USB-air pumps don't last more than a couple months outside, and changing them was very difficult.
I should have centralized the air to a single air pump.
What about the fish?
Honestly, I found most of the fish in my nano-ponds to be fairly boring. While they did breed, they all looked the same from the top.
The exceptions to this were the clown killies and the guppies. I'm not a huge guppy fan, but they were far more interesting to watch than most, because of their more vigorous activity and waving tails. The killies weren't so active, but they are pretty to look at form the top, with the silver dot on the top of their heads really grabbing attention.
I think if I were to do it again, I would definitely try platies, especially if I could find some interesting colors.
Hope that helps!