Natural ponds usually have some water running into them if only from time to time and it can escape in a variety of ways.
Garden ponds have an impervious liner and the stuff that gets in there decays and goes acidic. The quality of the water suffers.
Koi pools like mine have a bottom drain and the facility to remove all the crap.
(we are most insistent in that).
There you go. None of the course stuff even gets near my filters. The explanation is in the write-ups
Filter Pump Sump - YouTube
Koi Pool Sump Purging - YouTube
I've a facility to trickle water in (at the rate of a dribbling tap) and out automatically, I do it 24/7
This sort of thing isn't necessary for goldfish or frog ponds.
But it's just as important to remove the detritus from a gold fish pond from time to time. A trickle change will improve the quality of the water and the health of the occupants.
To keep a pond clear of detritus you can hire an aqua-vac, but unless it is done at least yearly, it may be difficult to clear it out without draining it.