Shell dwelling cichlids have become more aggressive
I have a 60 cm aquarium. It houses one pair of shell dwelling cichlids (Neolamprologus brevis) and 2 Lamprologus laparogramma. These 2 liked being close together in the beginning, but recently they have become very aggressive towards each other. We have many rocks with holes in them plus plants, but one of the fish always has to retreat to the water surface to be safe. What shall we do? More rocks, or keep the fish separately?
rocks are not the best choice in this case. I recommend plenty of empty snail shells plus bottom ground consisting of fine sand sufficiently thick to allow the fish to dig in the shells. However, it is advisable to keep the fish in a larger aquarium or to separate the species. Due to the high intraspecific and interspecific aggressiveness of lamprologine cichlids (except the unusually peaceful Altolamprologus), the capacity of the small aquarium is quickly consumed even if there are only a few specimens. Some harmonizing N. brevis or a group of N. multifasciatus are OK in a 60 cm tank - but a sufficient number of snail shells (edible snails are well suited; Neothauma shells are difficult to get) is by all means required. For instance, I cannot even recommend Lamprologus ocellatus for tanks less than 80 cm long - I am referring, however, to a tank for just one species without other cichlids!
The sudden rise of aggression among the L. laparogramma is likely to be related to adolescence and indicates that both fish probably are of the same gender (most likely males).
Background information: Shell dwelling cichlids originate from environments that provide very few resources. Sandy bottom does not provide geologically formed shelters such as rock crevices etc., the fish have taken to retreating into empty snail shells. Furthermore, there is usually rather little food available. They therefore need to defend their occupied territories - and they do so vehemently, even against physically considerably superior fish.
I also do not know whether the Lamprologus are males of females, or if it is a pair. How can I recognize the gender of these fish?
Outside courtship/when caring for the fry this is very difficult, at least if the fish are not fully grown yet. However, considering the experience with other cichlids it should be possible to differentiate the genders of adult fish according to the size and shape of the genital papilla (females have a much larger one, for obvious reasons).
Summary: I recommend to separate the species and by all means provide a sufficient number of snail shells!
Dr. Bodo Schnell