Do you think that’s what this is? Some kind of bacterial bloom? If the water parameters stay good, can this be something just passes or will it need a treatment like what you mentioned or perhaps some other kind of treatment?
It looks like a bacterial bloom to me. If its a new aquarium it may pass, if it's an established aquarium you may find a solution, that solution may be to reduce the number of fish, increase filtration, get better filter media, reduce feeding or increase water changes etc. Or you could fiddle with things for the next 12 months and find no solution. Finding a natural solution is obviously the best solution, but I wanted to put UV on the table as it will kill bacterial blooms.
I've got an overstocked aquarium that has the same issue. I fiddled with things for 6 months maybe. Saw some improvement but never completely resolved. 24 hours after installing UV, completely clear water. 5 years go by, and i knew the UV had stopped working because the cloudiness came back. The impeller had stopped running, and I couldn't get it running again, so I got a new UV and again 24 hours later, clear water. I'm fairly certain if I halved the number of fish my issue would be resolved. I don't have the same issue on other aquariums that aren't overstocked.
You havent given any details about the aquarium, size, stock, filtration etc. But it does look quite busy from the photos you posted, and the light on the bottom is probably making things appear worse than it is. And remember that your test kit is a home test kit and not all that accurate. It might be you are getting trace amounts of ammonia, especially after feeding, that your filtration isn't clearing immediately as it should. While these trace amounts may not be enough to register on a test, they would be enough to trigger a bacterial bloom. Is the cloudiness worse an hour or so after you have fed your fish?
I've had a look at your filtration media. It gets its surface area from it's porosity similar to seachem matrix or biohome. If it loses its porosity it loses a lot of that surface area and won't function as well. Ensuring you have a polishing pad before the filter media will help prevent the pores in the filter media from getting clogged up. Increasing filter maintenance including frequent rinsing off the filter media might help. Sintered glass media is often quite fragile too and tends to disintegrate quite quickly, but that's a different issue.
How much water and how much filter media do you have? You want to be looking for 1kg of filter media for every 100 litres of water.
There are things you can look at before considering UV, although some of those things are probably more palettable than others. And your filter media is certainly one of those things, especially if your problem after you switched it. Looking at the photos, it just looks like a smooth ring it doesn't look to provide much in the way of surface area, and these porous types of media don't tend to work as well as the manufacturers claim down to the porosity getting clogged up very quickly. A more traditional textured ceramic ring like biomax might give better surface area, and simple block of 30ppi sponge would almost certainly be better. Plastic pot scrubbers are excellent filter media to.
But UV will solve your issue.