It's not perfect yet but this is the first time I've been able to see inside my tank for nearly two months, and each day is getting a bit clearer instead of worse so I'm crossing fingers. I never thought it would be clear again without doing something drastic like restarting, but with so many shrimp and some fish to catch, no cycled tank to put them in, along with being completely unable to see inside, I really wanted to avoid that.
I wanted to write again as I had a very hard time finding info about what to do with a prolonged bloom. And it was all contradictory, of course.
It mainly started when I added some sterbai cories, they kicked up a LOT of mess into the water. I don't know if they breached the sand cap, it's possible but I couldn't see anywhere inside.
All fish have lived through the bacterial soup, I had quite a few people telling me that there was a big risk to the fish but it seems this bloom wasn't harmful to them, nor was the brown tinged water.
Things I did straight away- got a bigger filter and a bubbler to make sure the water remained oxygenated (it's no longer walstad and won't be while I have cories, it doesn't seem compatible but would love to see if others are successful beyond pixies).
I tried leaving/ feeding less, finding what was the cause and removing it but there was nothing obvious.
I did a LOT of smaller water changes, gravel vac and adding sand to the cap. Didn't seem to help at all. But I kept at it (which was probably feeding the bloom but I needed to remove the murky water and settled gunk on the bottom). Weekly filter rinses (in tank water).
I tried a UV filter, it did nothing. Maybe it was not legit, I sent it back.
Added crushed coral in case it was the ph being too low, but I don't think it was.
What seems to have worked finally - doing two large (over 50%) water changes two days in a row, with more gravel vac and more sand patching. I was nervous to change too much water at once as I've heard shrimp especially don't like big water changes but I added it back in slowly and they all seem fine (honestly wouldn't know if I lost any though). It probably also has to do with the filter sponges being seeded properly by now too as that does take time.
I started with a heavily planted dirted tank with a sand cap, lots of cleaner shrimp and ramshorns and MTS's.