Yesterday during water changes, it occurred to me that I’ve talked about the tanks in my fishroom but I’m not sure that I’ve ever shown them. I am fortunate to have enough space in my home for a designated fish room. This isn’t where my show tanks reside, but where my “work” tanks reside. By “work” I mean the tanks where I keep fish under special circumstances e.g., sick or injured, segregation for breeding or aggression issues, or even quarantine for new fish.
Because most cichlids exhibit aggression during breeding and territorial defense, a common solution to reduce such aggression in closed systems is the introduction of sightline barriers. This can come in the form of plants, rocks, wood, decorations, or even sand piles. The basic principle is that blocking the regular view of one cichlid from another will reduce aggression between the two. However, relying solely on sightline reduction to mitigate aggression in cichlids is often futile. Why?
Territory disputes? With both species only and community tanks, this can be a potential problem. It can be mitigated by overcrowding, i.e., having so many fish that no single fish can claim a territory. Even if your tank isn’t overcrowded, you can still sometimes ease such disputes if you move things around in the tank frequently (e.g., rocks, caves, decorations).
Though I never posted about it, I ordered some fish back in the summer of last year. In that shipment was six juvenile Julidochromis ornatus. I set up a new 75g tank that would become a Tanganyikan community tank. I put the new ornatus in that tank with plans for them to be an “anchor tenant.” Everything had been going beautifully with them and the other inhabitants (compressiceps, ocellatus, signatus, etc.)….until last night.
Frequent water changes are widely hailed as a key variable in the well being of aquarium fish, especially cichlids. However, for at least one species of angelfish, fewer water changes may actually be beneficial, especially if your angelfish population is somewhat dense.
According to an article published in the January 2018 issue of Applied Animal Behavior Science, frequent or large water changes in aquariums housing Pterophyllum scalare may actually increase con-specific aggression in this species. The authors posit that water changes modify cortisol and other chemical levels that these angelfish use to establish social status. Frequent and/or large water changes dilute these chemicals, which effectively disturbs the baselines that set the statuses thus requiring that the angelfish re-establish them.
Less water renewal reduces effects on social aggression of the cichlid Pterophyllum scalare. Gauy, Ana Carolina dos Santos et al. Applied Animal Behaviour Science (2018). Volume 198, pp. 121 – 126. https://doi.org/10.1016/j.applanim.2017.10.003.