Definitely better in a group. I had a grow out in a tank by itself once and it only came out when nobody was around. It would hide immediately when you came into the room and always showed stressed colors. It was like this for 3 weeks until I got some geos in there with him. Almost as soon as the geos went in, he stayed out in the open when I came up to the tank. The change was practically instant. So yes, get a group, preferably 3 or more. This will make them eat better and will in turn give you healthier, faster growing fish.