Hehe. Isn't it a "biotope?"
I have a species-only puffer tank, and I still enjoy the little guys immensely.
Most ppl do keep maintenance fish in a species-only tank. Plecos, otos, amano shrimp... that sort of thing, as long as they aren't threatened by the main species. I keep large amanos in with my dwarf puffers. No shame in it.
is a blessing, not a disease.