These pictures are at the point of overflow, because of the rain… so are normally with a little less water flow… The cut off buckets that you see, with water running into them, have several holes drilled through, and have a layer of lava rock on the bottom, with the floss, to catch any particles smaller than the holes, which are designed to hold enough water, to keep the rocks wet for beneficial bacteria growth… the lowest one, has the pipes coming out to water the plants, and overflow holes drilled higher, and bigger ( you can see water pouring out of them, as everything is at maximum, from the rain
Main filter is a 5 gallon bucket, with an extension, to contain the splashes, and keep the outside dog, from trying to drink out of it…holes on the bottom, and filled with lava rock, this sits in the barrel, above the sump pump, which pumps the water to the highest tank… and they all gravity flow back to the filter