It is interesting to observe that a lone Tropheus gets mopey even when the barrier allows view of the colony. The one that was injured swims with the rest but was mopey in isolation. Now the dominant male is in isolation and mopey.
Can't live with each other but can't live without each other.
Yes, these are highly social fishes that live in large groups in the lake, and they languish when kept alone in captivity. As you've discovered, just seeing conspecifics is not enough; they need to interact with them in a more substantive way, and those interactions form the basic fabric of the
Tropheus social hierarchy. Because intraspecific aggression is one of the dominant interactions among group members, the group must be relatively large, at least 10 individuals, and preferably two or three times that number, in order to spread the aggression around, and thus maintain the overall stability of the colony. We learned all these lessons the hard way when
Tropheus were first imported. At that time, if bloat didn't get them (inappropriate diet), then intraspecific aggression (inappropriate social environment) would. Here is a video from
Tropheus expert Pam Chin of
Tropheus in the wild, which provides clues on keeping them in captivity-
Interestingly, I have found that many Tanganyikan cichlids from diverse genera do poorly if they are kept in the absence of conspecifics. These include genera that are highly social (
Cyprichromis, Enantiopus, some
Xenotilapia, etc.) as well as genera that are more solitary or pair-oriented (some
Xenotilapia, Aulonocranus, Triglochromis, etc.). This is easily observed when brooding females, for example, are moved to isolation tanks: they do much better in the presence of one or two non-brooding female 'midwives' than they do alone.
These kinds of behaviors are what make Tanganyikan cichlids so challenging, and to my mind, so interesting.
