Not sure what I've seen here (notice the small grey patches in the water on the upper right half of the photos?). I suppose it's some kind of AS/water column interaction. I've observed it in rare cases over the course of some years.
Sorry for the bad pictures but as you can imagine the clouding happens quickly and disappeares fast in the current. Grabbed the camera and shot away without any fiddeling.

And no it's not a shrimp digging in AS which might have caused it and which could have looked similar. There was too much clouding and too much ground cover for shrimps to reach the substrate.

Congregations of bacteria is another idea which came to mind.

Best regards,
Detlef

So this just suddenly occurs?

And then wanders away on its own?

Might be a gas bubble burping out some CO2 etc, and then taking some dust up with it.

Regards,
Tom Barr

Due to some serious family affairs I've been away from computers for a couple of days. Sorry for late reply.

Yes, the clouding occurs suddenly without me doing anything on the tank.

And yes, the patches of haze can be observed two, three or more times with only seconds separated from each other and then never again for a very long time, may be months.
I might happen more often, I just do not know. Yes, it wanders away on its own quickly in the current.
Takes not much more than say 5 sec's to disappear dependent on how much current there is of course.

A gas bubble urging dust to raise? Good idea the clouding particles definitely come up from the substate and raise quickly to higher layers of water but no and I'm pretty sure,
there are no bubbles to be seen! All I can say is it happened last time just before the lights went out in the evening, with at least 30ppm of CO2 in the water
(4dKH fluid in drop checker), no conspicuous water param's as far I can tell, AS one year old, may be a week after some of the stems got a trim.

The hobby surprises me quite often I must say!


Best regards,
Detlef