If you have hard, alkaline tap water and you want a tiny cichlid that runs its own colony in a small tank, Neolamprologus similis deserves a place on your shortlist right next to its famous cousin. Similis is a shell-dwelling Tanganyikan, one of the smallest cichlids kept in the hobby, and it does everything the better-known multifasciatus does: it digs, it defends a shell, it breeds inside it and it builds a little society across the tank floor. The main practical difference is the look and the temperament, and both, to my eye, come out slightly in favour of similis. This is the species profile: what it is, how it differs from the multi, and how to keep and breed a colony in water like mine.
Similis at a glance
Neolamprologus similis is a shell-dwelling cichlid from Lake Tanganyika in East Africa, one of a small group of species that live their whole lives in and around empty snail shells scattered across the lake bed. A large male reaches around 4 to 5 cm and females are smaller, so the whole species stays thumb-sized. In the lake they occur in dense colonies over shell beds, each fish claiming a shell as home, breeding site and bolt-hole all in one.
Everything about the fish is built around that shell. It bolts into it at the first alarm, it excavates the sand around it into craters and ridges, and it will spend a startling proportion of its day moving substrate mouthful by mouthful. For something the size of your thumbnail, a settled similis reshapes a remarkable amount of the tank floor.
How similis differs from multifasciatus
These two are close relatives and are constantly confused in shops, so it is worth being precise. If you already keep multies, or have read my guide to Neolamprologus multifasciatus, similis will feel familiar, but there are real differences.
The clearest is the stripe pattern. On multifasciatus, the vertical bars stop at the gill cover and the head is plain. On similis, the fine vertical stripes carry on right across the head and face, giving it a striped-all-over look that is the reliable way to tell the two apart in a tank. Get close to the glass and the face is the giveaway.
Similis also tends to run slightly larger and, in my experience and in the wider hobby’s, a shade more sociable. Multies are famously feisty for their size; similis colonies often pack a little tighter with a touch less constant bickering, which makes them a forgiving choice for a first shell-dweller. Both fish want exactly the same conditions, so the choice between them is mostly about which pattern you prefer and which the shop actually has, since mislabelling is common.
Tank and water
Footprint matters far more than volume with any shell-dweller. Their whole world is the bottom few centimetres of the tank, so a low, wide 40 to 60 litre tank suits a starter colony well and a tall tank just wastes money on water they will never visit.
Water is where similis either fits your life or does not. Lake Tanganyika is hard, alkaline and mineral-rich, with a high pH, and similis wants the same. If your tap water is hard, you are in luck, and these fish are one of the best matches you can find, as I have covered in keeping fish in hard water. My own tap is liquid limestone and the shell-dwellers could not be happier for it. If your water is soft and acidic, be honest with yourself: you would be remineralising every water change forever, and unless you enjoy that routine, similis is a poor fit. The mechanics of the numbers involved are in GH and KH explained.
The substrate must be soft sand, and this is not negotiable. Digging is central to how similis lives, and even fine gravel defeats them, because they pick the substrate up in their mouths and spit it out elsewhere all day. Two or three centimetres of plain, fine sand is plenty. Do not bother scaping the floor carefully, because they will rearrange it within the week.
Then the shells. Empty escargot shells are ideal, cheap and the right size, and you want far more shells than fish. At least three shells per fish, heaped and scattered so they can sort them to their liking. A generous shell supply is the single best thing you can do for colony peace, because a fish with a spare shell nearby has no reason to fight over a neighbour’s.
Filtration should be gentle. A sponge filter or a small internal filter is plenty for the modest bioload of a handful of tiny fish, and you want to avoid anything that blasts current across the sand, both because the lake floor they come from is calm and because strong flow undoes the digging they work so hard at.
Stocking a colony
Start small and let the colony build itself. A group of five or six juveniles, or two males and three or four females if you can sex them, is the right beginning. Resist filling the tank on day one, because a colony has a structure and that structure has to grow into place.
The fish sort themselves into a loose, roughly matriarchal hierarchy, with established females holding the prime shell clusters and a dominant male ranging over a wider patch. New adults dropped into a settled colony are treated as invaders, whereas fish born into it slot in at the bottom and work their way up. So the cheapest and most peaceful route to a large colony is to buy a small founding group and let them make the rest. Expect the first weeks to be tense, with chasing and posturing while territories get drawn, and provided the shells are plentiful it settles into theatre rather than warfare.
Feeding
Small fish, small mouths, small food. Crushed flake works as a staple, with frozen cyclops and frozen or live baby brine shrimp as the treats that really draw the colony out of its shells. Cyclops in particular is well sized for them and doubles as a first food for any fry about the place, which in a working colony is most of the time. Feed modest amounts once or twice a day, give the food a moment to sink, since they are bottom-oriented, and watch it is not all swept into a corner by the filter before they reach it. The general principles are in feeding aquarium fish.
Behaviour and tankmates
For their size, similis are bold and endlessly watchable. Mine come to the front glass and square up to a finger during maintenance, and the daily entertainment is the digging, because no arrangement of sand is ever finished. Shells get buried, unburied and relocated, craters deepen, and a ridge appears overnight between two territories like a border wall.
My advice on tankmates is a species tank, full stop. A shell-dweller colony is a complete, self-running display and does not need company. If you must add something, the only sensible choice is a small group of peaceful open-water dither fish that occupy the upper layers and never contest the floor, nothing that digs, eats fry with enthusiasm or is large enough to loom. Every addition adds bioload to a small tank and pressure on the fry, and I have seen more shell-dweller tanks spoiled by ambitious stocking than by anything the fish did themselves.
Breeding
Breeding similis is a matter of getting the setup right and then leaving them alone. Once the colony feels secure, a female spawns inside her shell, tends the eggs there, and one day you notice tiny slivers of fry hovering at the shell mouth and vanishing into it when anything looms. The colony tolerates its own young, the mother guards the immediate area, and the fry graze on crushed flake dust and cyclops. There is no need for a breeding tank, no egg tumbling and no separating anyone.
The one bit of management the fish leave to you is population. A 40 to 60 litre tank supports a surprisingly large colony but not an infinite one, so when it starts to feel crowded, catch out a batch of juveniles and pass them on. Local fishkeepers and shops are usually glad of them. The reliable way to catch shell-dwellers is to lift out the shells the youngsters are hiding in, fish and all, since chasing them with a net is a losing game.
Common problems
Almost every shell-dweller failure traces back to the same handful of mistakes. Too few shells turns every shell into something worth fighting over. Soft, acidic water stresses fish that evolved for the opposite and no amount of good feeding fixes it. Gravel instead of sand denies them their main occupation. And buying too many adults at once forces a crowd of strangers to fight out a hierarchy from scratch in a small space.
Get those four things right, hard water, soft sand, surplus shells and a modest founding group, and similis is close to foolproof. If you would like the lived, day-to-day version of running a shell-dweller tank rather than the species profile, I have written that up as keeping shell-dwelling cichlids. Between the two shellies, similis is the one I would nudge a nervous beginner towards: the same tiny civilisation on your shelf, with a slightly gentler temperament and a face full of stripes.