Okay, thank you for your advice. Good to hear that peace lily can go together with shrimp. I tried and had the impression that it didn't work, but maybe something else was going on (I did have only the roots in). With mine the roots did start to go dark brown and soft, maybe some toxins got released there. So now they are in a bucket of water and I'll wait if they can get past the rotting phase and form some decent under water roots.
For my tank I did several things:
- I took out a few rocks to have more place for plants
- I decided to combine both of my tanks to one in the big one. This made it possible to take part of the plants of the small tank in the big tank. It also means I have one tank less to worry about. I did not break it down completely, it is now sort of a dumping site for plants/wood and stones I don't use. And a place where daphnia and other critters can grow. And a quarantaine for my last sick(?) dario dario (who will probably like the messy state it is in, with loads of hiding)
- I replaced a bigger piece of wood for a smaller one to have more place for plants
- I bought a test for the CO2. It measured 14mg/l after 5 hours of lighting. That is not extremely high is it?
- I did one big and two small water changes
- I now have a Ctenanthe Burle Marxii with the roots emersed and a grass lily and a small piece of pothos. Those are not supposed to be toxic.
On the left the corner where I freed up some space.
On the right the smaller piece of wood. It has a sort of tree shape and a hiding place underneath. One of my oto's is on the glass, I'm no expert but it seems to me his belly is nice and round so I think they have enough to eat even though the tank has not yet aged a lot.
After dosing the Esha2000 for three days my fish soon started to behave more normal. Still some movements of the mouth but far less and the few who were on the water surface stopped doing that. So my hypothesis is that an illness got introduced with the new fish. But hard to tell if I'm right
One of my dario dario did die after the first day of treatment unfortunately and the other one did not react to the treatment with the white spot he has but I'm still not sure if he is ill or has a little wound or something, he is in quarantine now. He was never gasping.
My amano seem a little bit less active, but I hope that's a coincidence, it's not that they're all completely inactive. The cherries are walking around doing their thing. Look at this charming little fellow, my first cherry kid growing up

. He now seems to feel that he is big enough to come out of hiding. Before yesterday I rarely saw him. Today I stuck the small piece of stem plant in the back in the substrate just an inch behind him and he didn't care at all...
Hopefully the trouble is over and I can start again enjoying the view of happy plants and livestock. I really love to observe my tank when everything goes well