The problem is they are skittish and need to be in schools. I've found that the tank size plays a very large role in how skittish they are. Small SDs can do fine in smaller tanks, but they grow fast and become very jumpy if not given enough room. I have four "regular" SDs, each about 5 inches, in my 90G and would like to upgrade to a 125G or 150G (plus get 2 more for a school of 6).