In 2018 I did build this one in the garden and it still runs, with a small change like a charm today. This concept could easily be created the exactly same indoors with houseplants. It's a planted sump at the same ground level as the body it filters.
🙂 It could also be at a lower level, gravity does it all.
gogogogo
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What i did change is the spray bar/trickle tube, this didn't work in the long run because it got pushed up with plant growth beneath it. I shortened this tube to only running water into the first pot, and lowered the substrate in this pot to prevent it from overflowing, to mechanically filter the water, the plants in all the other pots have their roots hanging in the water and don't need to get dripped from above.
There are quite a number of houseplants that would love to be in such a setup. E.g Ficus sp. Sphatifyllum sp. Monstera sp. Syngonium sp., Anthurium sp. and many more.
Anyway, this is the simplest and most effective maintenance-free filter I did ever build. It's made from epoxy treated plywood used in the building industry assembled with silicon like an aquarium, with sufficiently enough screws. Indoors it could be made from any type of decorative wood planks with a polyester/glass fiber inlay to waterproof it. For a big aquarium, I can also guarantee that building this is not more expensive than a cannister. The pots are pennies, the PVC tubing a few quit, the plywood was less than a 100. Making it from walnut to show off indoors would be a different story.
🙂
Anyway a filter like this with large houseplants would be a hell of a room devider.