I recall this/these issue(s) from other threads, but a couple of things need reinforcing.
I already suggested elsewhere that the panda garra be left alone, given the time and everything else here. Getting more of them means a much larger tank and few if any of the other mentioned fish. Leave well enough alone. If the garra becomes problematic, re-home it (or lose the other fish).
Shoaling fish as you know need groups, and for almost all species including those here that means 10 or more of each species. A 200l (52 gallon) tank is quickly going to become too full, so you should consider which species you can re-home, even if it means giving them to a store.
The need for numbers is programmed into the genetic blueprint for the species. The fish "expect" this, and it simply must be provided. And on this, there is absolutely no way any one of us can ever say "the fish are happy" or whatever, because frankly we cannot talk to them to find out. All we can be certain of is that researching the individual species needs and providing as close an environment to the habitat as reasonably possible is the only way to assume the fish are OK. You cannot go by fish actions/behaviours except when things become so bad the fish react negatively, and by then it is too late. Fish like all animals have one supreme instinct...to reproduce to ensure survival of their species, and they will do everything they can to "make do" or manage with any situation in order to achieve this goal. Fish that are swimming, eating and spawning may not for these reasons be in good health or stress-free.
When one acquires a "used" tank of fish it is a difficult situation if the previous owner did not understand things, as is clearly evident here. We have to fix the issues as best we can, and sometimes getting rid of "x" species needs to be done, depending. The poor fish are the losers nomatter what, but this is not your fault even though the responsibility to fix it is now yours.
