The pond is 900 litre, that's roughly 238 gallons. The pond is inside, at home in spare room that was never used before.
I always preferred sand as substrate because it doesn't collect as much detritus and I am a bottom fish lover....
I always put coarse sponges on the intakes and the intakes are halfway above the sand so I haven't had any issues with impellers. Two of the filters are 6 and 7 year old. There's a third one but its only been there for just over a year. I use the pre-filter sponges to protect the bio-media and it also protects against sand.
I can only see through the top but because the pond is round, the viewing angle is quite large, unlike a rectangular tank's top view. It's just difficult to picture and take videos but I'll buy an underwater camera one day. My phone has limited under water ability so I was able to take at least one video
In person, I am able to see the fish in great detail and a lot more than I was ever able before because they don't hide, swim right under my nose, and in fact come and beg for food on the side of the pond where I have a chair to sit and observe them. That applies for every fish in the tank besides the corys and kuhli loaches who never notice me

even during water changes
The barbs are doing really well. They have such beautiful colours. See a close up below. And they're great dithers for clown loaches. They ate my plants though,including my large anubias plants

Apart from that, really great fish to have, healthy as well. I've had no problems with them(or any other fish in the pond) and I raised them from fry size.
Generally my fish are way happier in the black pond than they were in a transparent glass tank. I understand its not everyone's cup of tea...I love mine though

Its worth it just to see the great difference in fish behaviour...
