Ok here is exactly what I would do
It helps in my opinion to have the tank look as natural as possible
Therefor only sea shaped rocks and coral and plants maybe driftwood should be placed in a natural way in the tank
And fish I prefer the fish to stand out above the decoration
So some different variety of small and big colorful fish I would add
Angelfish(2)
Clown loaches(1)
The Plecoptera you already have(1)
Neon tetras the best in my opinion 7-10
Giant or banded gourami(1)
All go along with each other and perfect for an exiting fish tank
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