Nano Cichlid Stocking Calculator

How to use the Nano Cichlid Stocking Calculator

A practical walkthrough for stocking dwarf cichlids in tanks between 75 and 300 litres — written by someone who has kept all four species covered here.

What this tool does

The calculator takes three inputs — tank size, dwarf cichlid species, and optional tank mates — and returns a complete stocking plan: a recommended harem or colony structure, a bioload score, compatibility warnings, and a setup checklist (caves, shells, filtration). It covers the four nano cichlids that actually work in home aquariums under 300 litres: Apistogramma, German Rams, shell-dwelling Lamprologus, and Kribensis. It does not cover the larger "American cichlids" (Oscars, Jack Dempseys, Severums) because those are not nano fish — see our Oscar care sheet for why.

Step by step

Step 1: enter your tank size. Pick the closest preset (75, 120, 200, or 300 litres) or type an exact value. Use the actual water volume — measure it during a water change, not the tank's sticker. Substrate, driftwood, and caves displace water; a "120 litre" tank usually holds 95-100 litres of actual water.

Step 2: pick your dwarf cichlid species. Each has very different requirements. Apistogramma want soft acidic water (pH 6.0-7.0), a harem of one male to three females, and a cave per female plus one for the male. Rams need warm water (26°C minimum, 28°C ideal) and are sensitive to nitrates. Shell dwellers are the odd ones out — they need hard alkaline water (pH 7.8-9.0, ideally with crushed coral in the filter) and a pile of empty snail shells. Kribensis are the easiest and most forgiving; they tolerate a wide range and breed readily in pairs.

Step 3: pick tank mates (or none). A species-only tank is almost always the better choice for breeding and for fish that show natural behaviour. If you want tank mates, the calculator offers the three that actually work: Ember Tetras, Chili Rasboras, and Pygmy Corydoras. All three are small, peaceful, and stay out of the cichlids' way — but each has compatibility quirks the calculator will flag. Rams at 28°C are too hot for Pygmy Corys long-term; shell dwellers' hard water is incompatible with the soft, acidic water Chili Rasboras need.

Step 4: click Calculate. The results card shows a harem/colony recommendation sized for your tank, a bioload score as a percentage of your filter's capacity, compatibility warnings for temperature and pH conflicts, and a setup checklist with cave counts, shell counts, and filtration sizing. Read every warning — they are not suggestions.

What the results mean

Bioload score. A percentage of your filter's processing capacity. Under 60% is comfortable for a cichlid tank. 60-80% is workable with weekly 30-40% water changes and a mature filter. Above 80% means you are one missed water change away from an ammonia spike that will kill your dwarf cichlids — they are far less forgiving than tetras or livebearers. The calculator will warn you above 80% and refuse to recommend above 95%.

Harem structure. For Apistogramma and shell dwellers, the recommendation is multiple females per male. A pair (1M:1F) almost always ends with the male harassing the female to death — the female has nowhere to escape. A harem (1M:3F) spreads the male's attention across multiple females and gives each female her own territory. For Rams and Kribensis, a bonded pair is the standard unit; the calculator recommends a pair in tanks under 120 litres and a pair plus dither fish in larger tanks.

Compatibility warnings. The four nano cichlids span a wide range of water parameters. Shell dwellers need hard alkaline water (pH 7.8+) that would slowly kill Chili Rasboras and Ember Tetras. Rams need 26°C+ water that long-term stresses Pygmy Corys. Apistogramma and Kribensis are the most flexible. The calculator will tell you when a mate combination is incompatible and explain why.

Common mistakes I see

Mixing cichlid species. A common impulse is to put an Apistogramma and a Ram together in a 120-litre tank "for variety". Within a week, one will kill the other — usually the Ram kills the Apistogramma, because Rams are surprisingly pugnacious despite their delicate appearance. One cichlid species per tank, full stop. If you want two species, get a 300+ litre tank with clearly separated territories.

No caves. Dwarf cichlids are cave spawners. Without a cave, they cannot establish territory, cannot spawn, and become stressed. Apistogramma want coconut shells or PVC caves (one per female plus one for the male). Kribensis and Rams want slate caves or flowerpot halves. Shell dwellers want a pile of empty escargot shells — at least one per adult, ideally two. The calculator tells you how many.

Skipping the mature-filter step. Dwarf cichlids cannot go into a freshly-cycled tank. The filter needs to be 8+ weeks old and ideally seeded with media from an established tank. Rams in particular will die within days in a tank that has any detectable ammonia or nitrite. The calculator assumes a mature filter; if yours is not, do not add dwarf cichlids yet.

Frequently asked questions

Can I keep Apistogramma in a 40-litre tank?

No. A single Apistogramma pair needs 75 litres minimum, and a proper harem (1 male + 3 females) needs 100+ litres. A 40-litre tank is too small for any nano cichlid except a single shell dweller colony of 4-6 fish.

Can I mix different nano cichlid species in the same tank?

Generally no. Dwarf cichlids are territorial and will fight other cichlids for cave space. The exception is a very large tank (300+ litres) with multiple distinct territories, but even then aggression spikes during spawning. Stick to one cichlid species per tank.

Do shell dwellers really live inside snail shells?

Yes — Neolamprologus multifasciatus and related shell-dwelling cichlids from Lake Tanganyika live inside empty Neothauma snail shells. The male guards a colony of shells; each female claims one shell as her territory and raises her fry inside it. In the aquarium, provide 1-2 empty escargot shells per adult. A 60-litre tank with 8 shells and 6 shell dwellers is one of the most behaviour-rich setups in the hobby.

Why does the calculator recommend a harem instead of just a pair?

For Apistogramma and other harem-spawning dwarf cichlids, a single pair in a tank usually ends with the male harassing the female to death. Multiple females spread the male's attention and let each female establish her own territory. A 1M:3F harem in 100+ litres is far more stable than 1M:1F in 75 litres.

What temperature works for nano cichlids and ember tetras?

Ember tetras tolerate 22-28°C, which overlaps with Apistogramma, Kribensis, and shell dwellers. Rams need 26-30°C minimum, so ember tetras work with Rams only if you keep the tank at 26-28°C — the upper end of the tetra's range. Chili rasboras and pygmy corys prefer cooler water (24°C max long-term) and are not ideal tank mates for Rams.