Quarantine - which way to go

[Beastije]

So, at this point I have 3 tanks. A large 360l to which I want to add new fish, at 26°C. Middle 54l tank, which has some old "leftover" fish and one brotia herculea, that is at 22°C, and a 40l shrimp colony also at 22°C.
If I were to buy 10 ember tetras and 10 otocinclus hoppei, which would be the way to go? I could temporarily move the brotia from the middle tank to the shrimp tank I guess, and add the fish to the established middle tank with the leftover fish, and in case of issues I would have to boil the substrate. Or I could add them to the shrimp tank, but in case of issues, how would I treat it, since medication stays in the algae.
Or I could split the tetra and the otocinclus between the tanks to quarantine and only move the brotia and maybe move the shrimp in case of issues before attempting to treat the tanks?
Overall a head scratcher, I have time before I am going to get the fish, but I want to be ready to have it figured out.
Which way would you go?

 

[GaryE]

In that scenario, something is at risk. You are one tank short!
You can take your chances and combine the new arrivals.
You can expose the older fish to danger.

Shrimp are med sensitive.

 

[Beastije]

Scary thing is, I have two empty tanks at home, but very old that would require heavy limestone cleanup, and I am also not sure where would I put the tanks, since they are both quite large and weirdly shape. One is a cube 45x45x45 cm and one is very low and narrow, 80x30x30 cm. I am not sure where would I even put them, and especially for ottos, how to set them up to have some algae and how long to keep it running to be absolutely safe before and during. I also think I only have one airpump which has not full flow anymore. What I absolutely dont have is a light and am not willing to spend money on it.