Ever since my brother started to put up his fishes at home, I also wanted to have fish spa also. By far, the only fishes that are commonly used in fish spas are the ray-finned fishes from the family Cyrpinidae. These are the Garra fishes or the so called Doctor Fishes or the Spa Fishes.
Garra Rufa Fishes — the Doctor Fishes or Spa Fishes (image from gstatic.com)
The most common features of these Garra Rufa Fishes — the Doctor Fishes or Spa Fishes are their slim body yet having a fat belly. And of course, their sucking mouth.