nebula:
I've recently had a pond built. It's shaped like a kidney bean measuring 4.2m long, 2.3m wide, 0.8m deep at the deepest. It has a shallow end. I'm not sure how much water it holds as it's an odd shape. If it were a rectangle and same depth throughout it would be ~7700L. So I'm guessing somewhere between 5000 and 7000. I'm experienced in keeping aquariums but don't know much about pond ecosystems.
There is a water fountain powered by a pump so that will introduce water movement. If I heavily stock the pond with plants and feed sparingly can I keep up to 3 goldfish with no filter?
Sonic:
You will at some point get a build up of gunge in the bottom of the pond, from leftover food, old leaves and flowers from the plants etc, so if you are prepared to keep on top of that, then 3 fish would be ok without a filter. When it comes to feeding sparingly, its a good idea to help with the start up of the pond, but you'll be risking hungry fish at some point, so don't rely on that to keep the pond clean, fish are hungry in the warmer months. You could use a fine net to net the gunge out when it starts to build up.
nebula:
Thanks Sonic. I will need to clean it out anyway due to trees nearby so I'll buy a net and go down that route. Maybe look out for a second hand filter at some point...
Sonic:
A 2nd hand box filter should be cheap and would be perfect in the longer term.
Si4geckos:
I'd say yes if you want to see the fish. No if you want to occasionally see a faint orange blob in a green soupy slop.
My mums pond had 2/3 fish in for ages. No filter. Never saw the fish as the water is too green. I've just built mine. Got a box filter with UV second hand and cheap and the water looks like it's just come out the tap.
Awesome viewing. Had the UV off for a week and could already see the algea building up and the water becoming less clear. Deffo find a second hand box filter if you can. Fair few around and they don't really degrade at all. I just put a new UV bulb in mine and we're good to go.