Is this the same tank? Can you post how it is set up so that things wash into it? Is the surface flush with the ground like a pond, or do leaves fall onto the surface from above? Does rainfall overflow the tank? In any event I bet the fish love the dynamic effects of the weather, very reminiscent of a wild biotope, that's awesome.
I have split bamboo branches and an old gutter piece, that catch and channel rainwater. into the tank
The tank does sometimes over flow during heavy, extended rains, there is a sump, which has a redundant continuous, emergency over flow to send any excess overflow water to the garden, or into a bucket.
I look forward to it overflowing, because it's a free, no effort water change, during long , heavy rains.
In the shots below, you can see the overflow sending water to the garden
When water reaches the hole in vertical PVC pipe (pic above), upper right hand corner, that overflow water ends up automatically coming out the tube, lower left of the shot above.
The tank is on a normal aquarium stand, not on the ground, its sump is slightly lower (right in the shot below)and placed off to the side.
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