Many cichlid keepers new to the hobby often want to know what the best shell is for their particular Tanganyikan shell dweller(s). The answer to that question isn't as straightforward as it might seem. For one, most cichlids in the hobby are captive bred, and thus shells must be introduced to their aquarium. Secondly, providing a variety of shells doesn't guarantee that your shell dwellers will select those that are endemic to the lake.
It's widely accepted that the shell of the Neothauma tanganyicense snail (pictured below), the largest gastropod in the lake, is preferred by most of the resident shell dwelling cichlids. It makes sense that these shells, which aren't very large at their maximum size, would be the shell of choice. They're large enough and abundant. However, for domestically bred cichlids that aren't naturally exposed to Neothauma shells, it means other options are widely available. Furthermore, the shell selection process of the shellies is more a product of individual preference, and there are many variables that affect that choice, especially when breeding - ability to move the shell, the size of the female relative to the shell, etc.
I have kept two shell dwelling species of Tanganyikans - Telmatochromis vittatus and Neolamprolgus ocellatus. However, I experienced other dwarf cichlids that will seek shelter in shells, specifically Altolamprologus calvus. I bred ocellatus and, while a bit selective, they didn't always choose a single shell species when presented with multiple options. Below are some of the shells I've made available to my shellies in the past.
With my N. ocellatus, I've had the most success using a Babylonia japonica, which is the shell at the six o'clock position above. Lots of shellie keepers advocate for Apple snail shells, but for some reason, my ocellatus just didn't find them attractive. A couple of the shells above are turbo species, which I thought might also be appealing but weren't. My juvenile A. calvus would seek shelter in the Apple snail shells (the large, dark shell at the two o'clock position above) but abandoned them once they grew too large to fit.
Needless to say, your shell dwellers may readily take to any of the shells you provide. They might also be picky and not like their choices. Shells aren't very expensive, so you might give them at least a few options and see what works for you.
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