A couple of weeks ago, I wrote a post about keeping mbuna with shell dwellers. Specifically, I mentioned that it can be done but requires some forethought.
What I omitted from that post is the danger to the shellies. Not from predation (because mbuna aren’t predators), but from the size and behavioral differences between two types of fish. Mbuna are rowdy and, while not large by cichlid standards, they’re much larger than shellies. Because mbuna do a lot of chasing and are pretty fast swimmers in short bursts, they can create issues. Specifically, they can overturn shells. This can be a problem if a shell is occupied.
One afternoon last week I did my weekly water changes. Everything was good in the 75g tank, which I describe in that previous post. Later in the evening while feeding all of the fish, I happened to notice one of the shells was upside down. That is definitely a position it shouldn’t be in. The photo above shows that particular shell (the algae covered muffin land snail shell) and it belongs to the dominant male ‘Lamprologus’ caudopunctatus in the tank (also in the photo above).
I reached down into the tank, uprighted the shell, and the male caudo came out but not exuberantly. Based on the fact that he didn’t dart out and across the tank, it seems he might have been a bit disoriented. The shell aperture was face down in the sand. Furthermore, the aperture is too small for him to turn around in or even rotate his body, so I suspect he was probably upside down for some time. He was probably head first in the shell, couldn’t back out, and couldn’t upright himself because of his size and size of the aperture. This would explain his rather docile exit from the shell once I uprighted it. I’m sure he would have survived for some time like that but, had that happened AFTER I fed the fish, I might not have noticed it until the next evening when I feed (I only feed once a day). That means he could have been in that position for 24 hours.
So if you decide to try and keep shellies with your mbuna, you might consider a way to anchor your shells, such as much more sand than I use, or otherwise prevent the mbuna from turning them over.