There is a lot of discussion regarding the aggressive nature of Tropheus. Many people fear Tropheus because they as so aggressive. My guess is that they either have the tank set up incorrectly, have too few Tropheus, too few Tropheus in a particular group or the sizes of the fish are a bad match.
Overall I do not consider Tropheus to be that aggressive. I have certainly had fish from Lake Malawi that were far more aggressive. One of the reasons I do not consider Tropheus to be too aggressive is that we watch all of our fish so often. We spot distressed fish quickly and react accordingly. We rarely get seriously injured fish, maybe because we pull them out so quickly.
Let us not kid ourselves Tropheus can be aggressive fish. Any fish, Tropheus included, will put into their mouths anything that will fit. If you put different fish of very different sizes, you are inviting a potential problem with aggression.
During the mating process, the male Tropheus will chase any fish that enters his area. I don’t really consider this aggression, as the intent is not to harm only to chase away. The chasing usually ends when the mating process ends.
It is true that Tropheus develop a social order or hierarchy. Therefore those at the bottom of the list are always at risk regardless of what type Tropheus you may choose to keep. Usually there is a dominant male in the tank at the top of the list, but it can be a female. (You have some real breeding issues if you have a female at the top of the list.) Aggression in a Tropheus tank is directly related to the aggression of the dominant male, in my opinion. There is far more aggression in a tank with a hyper dominant male than in other tanks. Tropheus tend to take out most of their aggression on their own type fish. That is to say, you rarely see an "Ikola" exhibiting aggressive behavior toward an "Mpulungu" for example.
Sick or injured fish drop to the bottom of the order and are at greater risk. You must isolate those fish or you will lose them. I once had a "Bemba" that I named “Black Knight”, in honor of the Monty Python movie, “In Search of the Holy Grail”. (Watch the movie and you will see why we named him that way.) This “Bemba” obviously lost the challenge to be the dominant male and he was a little worse for the wear from the battle. We took him out of the “Bemba” tank and placed him in an adjacent tank. There was not a cover or blind between the tanks so “Black Knight” could see back into his former home. While he recuperated, he did not stay away from the glass next to his former home, continuing to challenge the male he had lost the dominance challenge to. He believed he was in a fight to the finish over dominance and he never realized he had already lost the challenge. I am happy to say he recovered completely and has moved on to another home. Once a Tropheus has gained an advantage, they will not let go.
Outlined below is my opinion of the aggressive nature of each of the types of Tropheus.
First of all, I think that the tank setup has a large impact on the amount of aggression in a tank. Tanks that are full of rocks or other decorations are very pretty, but tend to have more aggression. In a tank set up that way, there are more areas that a male can try to use to set up his territory. (Plus it is difficult to catch holding females or fry with so much in the tank) Tanks with only one or two rocks or rock piles/decorations do not tend to have as much aggression in them. In that type setup, a male will stake out one of the areas and another will stake out the other. The remainder of the fish may stay in the middle and get chased out of each end, but the aggression generally will not be dangerous.
I have never kept annectens, so I can’t speak from personal experience as to their aggression, but I hear they may be the most aggressive.
It is generally believed that the brichardi group is the next most aggressive. That may be so, but the "Mpimbwe" I have kept are very docile fish. I cannot remember any “Mpimbwe” being killed due to aggression in that group. The brichardi do not seem to exhibit any real outward signs of aggression toward their own. Aggression in a brichardi tank is more of a “stealth” aggression. You never see them chasing each other, but the next thing you know, you have a seriously injured fish. Brichardi do seem to overshadow moorii if placed in the same tank.
Many people consider duboisi to be aggressive as well. I believe them to be less so than most think. They tend to do very little infighting. Usually when you get a good group the order seems to get set and varies little after that. They all seem to know their place and don’t move out of it. I do find duboisi to be a bit more fragile than the other groups. It seems if you upset their order, the whole group suffers. duboisi don’t seem to pay much attention to their tank mates, kind of like they are oblivious to it all.
Moorii seem to create the most frequent occurrence of the hyper dominant male. I have had more occurrences with aggression toward their own kind in moorii tanks than any other type. The hyper dominant male will slowly take out the lesser males in the tank. I have never seen them kill them all, just some of them. I believe that there is more territorial aggression in these types because of the hyper dominant male issue.
The Sp. Red seems to follow the same lines as the moorii, although they tend to ignore their tank mates more along the lines of the duboisi.
Sp. “Black” has a reputation for being aggressive. I believe that there is more overall aggression among sp. “Black” than with any other type. What I mean by that is that more of the fish in a sp. “Black” tank will exhibit aggressive tendencies than in a similar tank of another type. You notice a lot more chasing, bumping and lip locking in sp. “Black” than you do in other groups. It is common to see male and female sp. “Black” with white lips from lip locking. In spite of all the obvious aggression, my experience is that they may appear to be more aggressive, but the aggression does not seem to go very far, that is very few fish die from it. They seem to act like children playing, lots of shouting and gesturing, but no real physical harm. This type fish seems to breed better than the other Tropheus, probably because the overall aggression allows a dominant male to emerge.
You can, and will, have aggression in any Tropheus tank. That is good, because you will not get the fish to breed well until someone takes some control in the tank. Most of the aggression is directed to their own kind and does not seem to cross types.
You must be careful to get the right number of fish in the tank to lessen the aggression. If you have too few, you are at risk of losing fish, if you have too many, you are at risk that the breeding process will not occur properly. I cover this issue in another article on “How Many Fish Should You Put in a Tank?” Suffice it to say, too few fish is far worse than too many fish.
Overall, who is the most aggressive? I can’t really say. I think you will have more aggression in a sp. “Black” tank, but more deaths from aggression in a moorii or sp. “Red” tank. Again, rarely do they attack other fish; they concentrate on their own. I do not hesitate to mix the groups, all things being equal.
Generally speaking, when mixing the groups, the sp. “Black” and brichardi tend to overshadow the moorii and the sp. “Red” to a lesser extent. They will breed more than the moorii in the same tank. Brichardi and sp. “Black” do not seem to have the same impact on each other, they act as if they were equals. Duboisi seem to go along and ignore their tank mates, maybe even overshadowing the moorii, but only slightly. sp. “Red” also seem to be oblivious to their tank mates, but not as much as duboisi.
If you experience excessive aggression in your tank you can try a few things. Try taking out all of the decorations from the tank, turning off the lights, covering the tank for 24 hours or more and then seeing if they will start over. I have also had some success with putting tall rocks in the middle of a tank to eliminate the straight lines in the tank so as to give the chased fish some turns or curves to go around and avoid some of the chasing. Also giving the chased fish some areas to hide briefly can help. Small pots on their side will work. Finally, if all else fails, put the aggressive fish in “Time Out”. We use a net breeder for that purpose. You will be amazed, but it actually works. Try it yourself for a day and see what happens.
Finally, please remember that this is not scientific; I am only passing along what has worked for me and for others I have spoken with. I don’t guarantee any of the ideas in this article will work, but they have for ma and others. We are not scientists and this is not a perfect world, so we can’t always get it right. These fish are living beings so they will do funny things occasionally.
I hope you have enjoyed reading my ideas. Happy Tropheus keeping!