Just for future reference some medications I have personally used for all your issues has been fritz malachite green for the white fuzz, hikari ich x for ich, and api general cure for the white stringy poo. I almost always use general cure when buying a new fish just to prevent the parasites...
You should add some plants. The decaying plants should be good for bio films and I would add a fair bit more wood. Tannins help to calm fish and keep ph lower where plecos like it.
Bio films and algae is what the baby bristle nose should feed on at first.
For my pea puffers and Amazon puffers I use hikari ich x for ich, I use api general cure for internals and I use api fungal for fungal. These are meds I have used and have had success with just for future reference
Catfish in pic 2 is a gulper cat if I'm not mistaken. The multiple catfish in the third pic are some sort of wood cat not sure which and the loach in that pic is a berdmores loach from what I can tell.
Idk what these are but that is wild. Is it an indoor aquarium? I am just curious how they got in there. What size tank is it as well? If its large enough and it is worrying you maybe buy some kind of fish that would snack on a little larvae.
Get some seachem prime and doese a recommended dose. Continue to waterchange every day for a week and then test it at the end of a week. You may have started the cycle when u actually added the fish adding some nutrients to the water. Not sure though.
Just keep a close eye on everything. Most...
Yeah. Probably a pond/bladder snail. Ramshorns and pond snails are super common to have ride in on plants. That's how I got most of mine. I do have Amazon puffers so I ask stores to give me any pest snails they have and dont want whenever I go.
That's a ramshorn snail. They breed relatively slow for what people consider pest snails and help a lot with cleaning up dead plant matter and left over food. I keep them in any tank I can. What fish are you putting in this tank?
If you get some clove oil and put some clove oil in water and just let him sit in there for a few hours. People use it to anestazise pufferfish to trim their teeth but you can use it to euthanize. They nock out and then just stop being able to breath