Sound like my water. Ick.
So I was running 11 tanks all planted for a few years. All different setups. About half went through a MASSIVE diatom outbreak that lasted no less than 4 months and all resolved differently. I give 8 weeks for removal and natural balance before intervention. 3 resolved slowly with just a continuation of that. 2 required removing some cheap substrate I'd tried (I removed entirely one and capped the other with a sand due to plant mass). 1 I tried everything, I removed and replaced substrate, added and removed plant mass, tried products, changed lighting, added co2 and removed, changed a huge array of circulation and filtration techniques.... I still have diatom disaster tank now for a bit over 5 years others have been slowly torn down as a downsized die to personal constraints.
Diatom disaster tank after almost 3 years..... I bought some hefty totes and moved out the fish and threw away everything. Decor, plants, substrate, filter media, all of it.... scrubbed the tank and sat it on the patio next to my totes of fish for a couple months. Weather changed and I brought it in set everything up same filters with new media, all new plants from existing tanks, all new substrate though a large portion of the same as before just unused, seeded my cycle and added fish from the totes over the next couple weeks. Honestly not much changed, biggest change was adding laterite powder to my substrate (I sometimes do sometimes don't it wasn't new concept for me here) and a shorter siesta on lights. Also while I was down I went to one brand of ferts for all tanks though that shouldn't matter as I mix and dose dry ferts anyway I just wanted to order from one place instead of two. NOTHING. not a single dream of a diatom and I'm a week shy of 9 months running now. Instead I run a fine line with BHA on this tank lol can't neglect canister maintenance a week or delay water change day or it pokes up somewhere lol but I'll take the occasional h202 in a syringe treatment over diatoms for eternity any day especially when I know I was the slacker lol.
Have no idea of that's at all helpful but it's a short version of my story and I know I tried everything and having 30 years in the hobby I'd never seen anything like it and I was at a total loss lol.
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