I have a 75 gallon planted tank with 20 tetras and ~90 red cherry shrimp (RCS). Everyone in the tank gets along well and I started with 10 RCS and they keep having babies, which is great. The tetras aren't aggressive and only occasionally will nip at the shrimp if they are swimming during feeding time, but only briefly and they don't chase the shrimp once they realize they aren't food. I want to add 20 or 30 more tetras to the tank but I haven't added anything new to the tank in over a year. Should I have any concerns that the new tetras may behave differently and could be aggressive towards the shrimp? Or can I assume that since there is already a school of tetra in the tank that the new tetras wouldn't adversely affect the behavior of existing tetras and, more likely, will follow their lead and leave the shrimp alone?
I've also considered getting the new tetras and setting up a quarantine tank and then every few days take 3-5 from the quarantine tank and place them into the main tank. The idea behind this is the smaller number of new tetras would join the current school of tetras and fall in line instead of adding such a large number all at once and possibly having some chaos.
I may be over thinking this as I selected tetras for my RCS tank because they are not usually aggressive. Any advice is appreciated.