Yesterday I finally got round to making the barrel pond I've been wanting for ages. I drained the water already standing in the barrel then created a substrate of building sand and pebbles. I pushed some oxygenating plants into the sand, stood the reeds on a brick, then started putting the water back in as well as topping it up. As soon as I filled it it became super dusty, from the sand.

I am hoping the dust will settle on it's own but there's been no noticeable change at all overnight. There are oxygenating plants under the surface which presumably won't survive in such murky conditions. I also put a small pack of daphnia in, as well as whatever little critters were already present in the standing water.

Will it settle on its own? Is there anything I can do to help purify the water? I've read that watercress can be good. Or should I just just drain it (whilst straining out the critters) and refill with fresh water from the water butt?