@igorisujin,
Please don’t give up.
Perhaps you did too many and too large water changes for too long that stripped off the nutrients from the water column. There was no surplus so to speak for plants to utilize. It’s alright to do daily WC but the way I see it they should be no more than 5-10% of the total volume with the weekly one at 50%.
But the most obvious issue is the Co2.
You’ve got to make that work. BBA is mostly (Or almost always) from fluctuating levels of Co2.
HC will melt from low co2.
Most people have enough light over their tanks;
Ferts are easy as well. Plants usually tell you when they’re hungry.
But get co2 wrong, especially with light on the higher side and it’s all downhill from there on....
I hope you can get this tank back on track.
Good luck to you!
Thanks Andrew. I was working off the basis that the more water I change, the less ammonia is sitting there (from the aquasoil or deteriorating plants) for the algae to get hold of. I stopped changing the water for a couple of days, but due to the increase in diatoms I decided I had to suck them out. Once things have stabilised a bit, hopefully I'll be able to reduce the frequency a bit. a 5% water change could almost be done with a single scoop of a coffee mug!
Agreed, it has to be co2 in your case. 🙂
spot dosing bba with liquid carbon helps, diatoms are easily cleaned by shrimps and snails, good luck 😉
Yeah, I can't get hold of any in Japan - or at least I haven't seen any available. I would normally ask family in the UK to send some bits over, but I won't do that right now. Not a good time to be asking family to send a fish tank care package across the world!! There may be a similar product here that I just haven't found yet, but the Japanese-language BBA guides don't mention it. They focus on dirty tanks and CO2 (or plug the ADA BBA remover stick thing). Another thing that was mentioned was vinegar (酢), but I haven't tried it yet. There was a warning on that blog that it can damage surrounding plants.
Anyway, I sat down for a couple of hours yesterday with my tweezers, tediously removing as much as I could from the rocks and wood. If it comes back, I'll know I haven't solved the problem yet.
The stems are starting to recover from their trim 10 days ago, which is a lot slower than the last time. But at least the new growth seems OK, even if each stem is growing at a different rate. I may do well to replant the stems near the front, as they're not so pretty in the lower parts.

As I said, I spent a long time on the BBA/diatoms. It's a lot better than it was, but there's a way to go.

The HC is pretty ugly (with a few healthy nodes), but the hairgrass seems to be doing OK. It won't be the end of the world if the hairgrass takes over this section completely. The new Hydrocotyle leaves aren't too bad either. I cut off the vast majority when they diatomed-up and melted.
The moss isn't too bad - a little bit of diatoms tangled up in there and it's not as green/clean as it was, but it's not too bad. Hopefully at the next trim the new growth will be nicer.

I'll wait and see now how the situation goes this week - if the algae returns and if the plants continue to recover.
Changes made since plant melt and algae outbreak:
Added second HOB filter (ugly, but cheap and makes water move).
Switched back to the DOOA diffuser, but as I have a second filter now, I was able to put it directly in the flow. I also increased the bubble rate to compensate for it being less efficient than the airstone. It's just prettier, and I want to use it if I can.
Lowered the N and P dosing back down to the minimum one squirt, and hoping that the Aquasoil is sufficient.
Lowered the Do!Aqua K/Micro dosing down to (1ml/day). I had been slightly overdosing, as I was told to do so by the shop here.
Cut the lights down a bit. I can't give a percentage, but the visible intensity is reduced. I'll leave it like that and see how it goes. I don't know the PAR rating.
Thanks as always 🙂