Black 'dust' at the bottom of the pool

Hi I hope someone can help with this problem as we have never owned a pool before and know nowt about them. We inherited a small above-ground plunge pool from previous owners; we were told the sand filter was new but the pool had not been used for about a year (probably more like two). We fitted a new liner, filled up the pool . . . and that was the last time we saw it clean. It accumulates a fine black 'dust' on the bottom, which clings together in little clumps and collects along the seams, but when you disturb it it dissipates into the water. Don't know where it comes from - does it fall out of the sky? Have tried backwashing, and wasting the water after vacuuming, repeatedly. Assuming it was coming out of the pipes or the sand filter, we tried a product delightfully named a Slime Bag, you attach it to the return when filtering and it purports to catch any fine particles (down to 1 micron) coming out of the return. We used this for a week, the water became extremely clear but the problem persisted. During the past few days we've been using a secondary pump to try to hoover up the dust from the bottom without returning it to the system. There has been some improvement but the problem keeps on returning. Any ideas please anyone - what is it and how can we get rid of it?

Dory I was down in the Perigueux last week and a pool down there has some Sahara sand silt which was brought in by the rain, reddish brown and very fine so it passes through a zeolite filter which filters much finer than a regular sand filter. Letting it settle and vacuuming it to waste rather than through the filter is often the preferred method of removal.

Oh dear, harvesting has not started yet here and we have wheat fields next to us!

The slime bag caught something because you can see it's discoloured round the edges, but it looks brown rather than black. You are meant to rinse it with a hosepipe every few hours and it's difficult to tell if anything comes out.

We do have a lot of trees and I wonder if it could be a double problem, something in the pipes or filter and stuff falling in? There has been a lot of wind and rain over the past few weeks

Welcome Dory,

This is an interesting one. so did the slime bags catch the black dust or did it still occur whilst the slime bags were fitted?

It is harvesting time around our way now and very fine dust is in the air whilst the wheat in our case is cut. When this type of dust gets into the water the chlorine can oxidise it turning it black, could that be the source?