very small urban pond - fill via roof runoff, use for irrigation, and?

For some reason I really want a little pond in my yard, it would be pretty small, maybe 10'x6'ish?
I really dont want something that I need to bother filtering etc, am willing to do aeration like with a solar aerator.

Would be great to have something like a few fish or attract amphibians but am not sure about how that would work if I also use the pond for irrigation?

I kind of wanted to use it to hold water from roof runoff, maybe "fertilize" the water with fish but then want to use that water for irrigating my garden. Would the regular draining (not all the way of course) and refilling of the pond be too much disturbance to realistically have fish?

I was alternatively thinking about a duck or two but again, how to get clean water into it and get "fertilized" water out of it? I am hoping for a setup that, say as it rains, empties the fertilied water into maybe a secondary pond and the primary pond simultaneously fills with "clean" rain water... obviously I have no idea what I am talking about but am really hoping for some ideas!

Since your headline says "urban", something to think about. In the city there are more people wondering around. You'll want to be sure someone, particularly children, don't fall in and drown. In some places it is called having an "attractive nuisance". It means (in some places) that if you have something that attracts people or pets to it, you could be liable if they get hurt or worse, even though they were trespassing on your property. Where this law is in effect, even putting up 'Keep Out' or 'No Trespassing' signs would not necessarily absolve you from liability or lawsuit.

It's a good idea. I inherited a little pond that's somewhat smaller when I bought my current property. Fed by water off the roof.

We threw in some feeder goldfish (there's no danger of overflow to a natural waterway). We feed them a bit of fish food and chopped slug pate, and they graze on algae and mosquito larvae for variety.

Salamanders and frogs find their way in. I make sure there's a wood ramp so they can also get out.

The water feeds the adjacent barrels with tomato plants. Since it's been "improved" by the fish, it works well.

Overall, it has proved to be a great resource. The neighbouring kids come over to feed the fish, and we chat about gardening. I only wish it was three times the size.

I'm in the first year of a similar project.
My "pond" is a ~8 foot diameter stock tank.
It's on a lot with no buildings, but I already have ~5 inches of water in it.

I might add goldfish, koi or mosquito fish, but tadpoles or polywogs might do more for pest control plus many of them are well adapted  to temporary pools of water.
I am very interested in growing duckweed and or azolla in the pond, for their value as green manure.
I also want to use containers filled with wicking medium to grow in, just plunked in the pond.
These, plus a bevy of floating planters made from old coolers would be planted with  willow and other cuttings.
I plan on building a solar powered trickle filter that consists of a slow sand filter topped with biochar fed continuously by an airlift pump and populated with Red Wrigglers.
As the biochar gets befouled it would be removed, and used as a soil ammendment.
The filtering is to remove particles while retaining nutrients, thus allowing the use of ollas.



Keeping ducks primarily for their poop water is a big commitment.
I think keeping ducks out of a pond will be difficult,  but a closed top clean water tank that refills a duck pond might work.
A half barrel with a float valve could  sit in  a baby pool full  of sawdust or biochar.
The baby pool would drain to the garden.
All the poopy water the ducks spilled would be filtered by the sawdust or biochar.