OK, finally getting around to an end of summer update. To begin with, I kept fighting to turn this thread into an article. Every thing I tried, though, came out as a gardening vice fishkeeping article. My apologies to you, Gary, for not being able to turn your advice and encouragement into something workable.
On the terrestrial side, we did add some buildings, play with the foam "beach," and dicker with different plants. The pond is really blending into the scenery and the broader miniature world in which it sits.
On the wet side, this summer, a scorcher, we made it through with no population crash. I just let the hyacinth cover the surface, and the temperature difference was palpable. I just cut the hyacinth population in half, so my little dwarf lily now seems able to compete enough to try and throw out some blooms! Yay! As things cool, I may experiment with wet footed plants, with some sort of tray anchored to the "rock" (foam) shore. I did not experiment with animals beyond the guppy colony. For one, guppies seem to be thriving. Why mess with it? For another, the pond's utility has lent an emerging name to this railroad / harbor town: Dogwallow. The picture below shows why:
The pond has also become a spot for the kids to interact with...everything. The guppies seem to be OK with the catch and release program, pirate ships, plastic scuba divers, etc. A more useful interaction resulted in a much cleaner pond...
Anyway, I don't want to risk more delicate creatures given the activity of the humans and canines around them! Also, as a goal for this whole project was to keep it at an age appropriate level for the rest of the family (Translation: it could not just be "Dad's pond."), maintaining this in part as an outdoor classroom is a priority.
I'll keep this thread active as warranted. As the temperatures cool to the mid-70s in the deep, dark winter, I am sure I will be able to generate new ideas for it!
Aloha,
Eric