Reddit mentions of Rustic Three Tier Apple Barrel Outdoor Water Fountain

OK so I just set up this small patio system, as a learning experience. So far I like how it looks and sounds! Plan is to build a larger one (maybe 100gal) if all goes well here.... assuming my patio balcony can handle 100 gallons.

I used this cheaply made Chinese fountain (it was $110 when I bought it; I wouldn't buy it now at any price but would build my own, now that I see how it works). It has a pump in the bottom that runs water through a tube to the top barrel, which overflows to the second, which overflows back to the third. Plastic lined throughout. Unknown toxicity....
https://www.amazon.com/Rustic-Three-Barrel-Outdoor-Fountain/dp/B004V99HXW

There is hydroton in the top two layers, held in by netting or black permeable 'grow bags'; the bottom layer has 3 small goldfish, a couple rocks, an aquatic plant and one nerite snail. I started with a few gallons of water from an established aquarium.

Basil and watercress are doing fine, the others I did not expect to do well frankly (fish are very small!), but tomatoes doing better than expected - flowering and setting (one!) fruit, and the cucumber made some flowers but leaves are yellowing a bit.

Lessons so far:
There is not enough depth at the top compared to the 'spouts' to keep a top layer of hydroton dry. Will have to make overflow holes from the top two lower down, if/when algae becomes an issue.

It's set to a 15-min-on-per-hour cycle using a timer. After setting it up realized the top two barrels would not actually drain, as designed!.... so drilled a small hole (siliconed in a small tube) so that each barrel empties slowly through its bottom as well; when the fountain stops it seems to stop trickling at about the 30 minute mark, and starts up again ten or 15min later.

Seems to have iron deficiency, not sure about other nutrients.... My main goal is to grow greens that you can harvest leaf by leaf, such as bok choy in the winter, rather than fruits like tomatoes here, but not sure what to grow in the heat of summer besides basil....

Have not figured out any good way to incorporate solids management in this kind of design. Should probably at least find a foam filter of some kind to put over the pump intake