Apistogramma agassizii UK: Care, Strains & Honest Buying Guide

Why this guide exists

You searched "apistogramma agassizii", which tells me you're past the beginner stage and looking at one specific dwarf cichlid — and you've probably already noticed the problem. Half the results lump every Apistogramma together as "dwarf cichlids, soft water, done", and the other half can't even tell you which apisto is in the photo. Neither helps you with the two questions that actually matter: is this the fish I think it is, and can I keep it in my water?

I'm Dr Aisha Rahman. I hold a PhD in ichthyology and I review the scientific claims in every guide we publish — particularly anything that touches water chemistry or fish physiology, which is most of what makes or breaks an Apistogramma tank. This page is the answer I'd give a keeper who messages us saying "I've kept rams, I've got soft water, I want something with more personality — talk me through agassizii."

A male "Super Red" — one of the line-bred ornamental forms. Note the dorsal fin: it runs low and even along the back, and the tail comes to a soft point. That silhouette is the single fastest way to separate agassizii from the crested cockatoo apisto. Product photo · our warehouse.

Five things most UK guides never tell you

• It probably isn't one species. A 2020 study in Aquatic Conservation concluded that Apistogramma agassizii is "a geographic mosaic of potentially tens of species" across the Amazon, and that it has one of the widest ranges of any Apistogramma ^[2]. The friendly "Agassiz's dwarf cichlid" on the label is really a whole species complex wearing one trade name.
• Populations diverge over astonishingly short distances. A follow-up study found "exceptional genetic differentiation at a micro-geographic scale" in agassizii from the Peruvian Amazon — fish from rivers close together can be genetically very distinct ^[3]. That's why serious breeders keep localities separate and refuse to mix wild lines.
• Wild fish live in water that would alarm most keepers. Their blackwater habitats can run to a pH of 3–4 — extraordinarily acidic — yet tank-bred stock is described as "relatively unfussy" and thrives in far more moderate, soft, slightly acidic water ^[1]. You do not need to chase pH 3 at home; that's a wild extreme, not a husbandry target.
• It was named in 1875. The species was described by Franz Steindachner in 1875, honouring the naturalist Louis Agassiz — so the "Agassiz" in the common name is a person, not a place ^[1].
• They will hunt your shrimp. Apistogramma are substrate-picking micro-predators, and agassizii will eat dwarf shrimp and shrimplets without hesitation ^[5]. Lovely as the idea of a shrimp-and-apisto tank sounds, the shrimp lose.

Apistogramma agassizii vs the cockatoo apisto: tell them apart

This is the comparison that stops you buying the wrong fish. Both are South American dwarf cichlids sold as "apistos", both want soft water and harem keeping — but they are different species with a different silhouette.

If the fish has a flat dorsal and a pointed spade tail, it's agassizii. If it has a spiky raised crest and a fanned tail, it's the cockatoo ^[4]. For the full cockatoo profile, see our Apistogramma cacatuoides guide; for the genus as a whole — every apisto we stock and how the groups differ — start with the Apistogramma overview.

The strains we currently stock

Like most popular dwarf cichlids, agassizii is sold both as wild-type collections and as line-bred ornamental forms. The Super Red, Fire Red, double red and gold strains are stabilised aquarium lines selected for colour intensity — they are not wild varieties, and because wild agassizii vary so much by locality ^[2], there's no single "correct" wild look to compare them against. They're the same fish to keep; you're choosing a colour, not a harder animal.

How many to buy, and the harem rule

Agassizii are not shoaling fish — they're territorial dwarf cichlids — so the stocking logic is different from a tetra. The standard structure is a harem: one male to two or three females ^[4]. A single dominant male will claim a territory and court each female in turn; giving him several females means no single fish absorbs all his attention, which is the usual cause of a stressed, hiding female.

A lone pair can work, but only in a tank with enough broken sightlines — plants, wood, leaf litter — that the female can get out of view when she wants to. Two males in one tank needs real space (90–120 L and up) and a floor divided into territories neither can see across, or the subordinate male will be relentlessly pushed into a corner ^[5].

The water question: why UK keepers must check their tap

Here's where agassizii flips the usual British advantage on its head. The hard, alkaline tap water that suits livebearers and many community fish is the opposite of what this species wants. Tank-bred agassizii are relatively unfussy and do well across roughly pH 5.0–7.0 and 0–12 °dGH ^[1] — but much of southern and eastern England is supplied with water classified as hard to very hard ^[6], well above the soft end this fish prefers, and at a higher pH than is ideal.

That doesn't rule them out — it just means soft-water keepers have the easy ride here, and hard-water keepers need a plan. The cleanest solution is to cut your tap with RO (reverse-osmosis) water and remineralise lightly to a low hardness, then let botanicals (catappa leaves, alder cones, peat) gently acidify the tank. Whatever you do, prioritise stability over hitting a number: a steady pH 6.8 is far better for the fish than a pH that swings between 6.0 and 7.5 as you chase the textbook figure.

Tank mates that actually work

Agassizii live near the bottom and defend a territory there, especially when breeding, so the ideal companions occupy other layers, stay peaceful, and share the same soft, warm, acidic water. The classic combination is a dwarf cichlid below and a shoal of small dither fish above to draw it out and signal "no predators about":

• Cardinal tetras — the textbook dither fish for South American dwarf cichlids; a soft-water, blackwater species that keeps to the mid-water and brings a nervous apisto out into the open.
• Pencilfish and small hatchetfish — upper-water shoalers that leave the substrate entirely to the cichlid.
• Corydoras catfish — peaceful substrate companions, though in a breeding tank an active group of cories can stress guarding parents, so judge by tank size.
• A single male German blue ram — a fellow soft-water dwarf cichlid; see our German blue ram guide for whether your tank is big enough to give each cichlid its own territory.

Avoid: dwarf shrimp (they're food ^[5]), boisterous barbs, and anything that competes for the bottom or wants hard alkaline water.

Watch: a planted blackwater-style community

Transcript / what you're seeing (0:00–0:20): a heavily planted aquarium with small fish cruising the mid-water while the lower layers stay shaded and broken up by wood and leaves. That structure is exactly what a dwarf cichlid needs — the open mid-water gives dither fish room to shoal, while the shaded, cluttered floor gives each apisto a territory it can hold and retreat into. A bare, brightly-lit tank does the opposite: it leaves a territorial fish with nowhere to feel secure, which is when you see hiding, clamped fins and stalled breeding.

Sexing and breeding: a cave spawner with a guardian mother

Sexing mature agassizii is usually straightforward: males are larger, more colourful, and have longer, more extended dorsal and tail fins, while females are smaller, plainer, and turn an intense yellow when in breeding condition or guarding fry ^[4]. That yellow female is one of the loveliest sights in the hobby.

They are cave spawners. Give a pair a small cave — a clay pot on its side, a coconut shell, a purpose-made cichlid cave — and a conditioned female will lay her eggs on the cave roof. From there the roles split: the female guards and tends the eggs and fry, fanning them and herding the wrigglers around the territory, while the male patrols the wider territory and keeps other fish away ^[4]. Soft, warm, acidic water and a steady supply of live food are what tip a settled harem into spawning.

A "red dorsal" male. Even on a heavily line-bred colour form, the dorsal fin keeps the species' low, even profile — there's no spiky crest. This is the trait to fix in your mind: it's what separates agassizii from the cockatoo apisto at a glance, in any colour.

What to look for when you buy (anywhere)

Whether you buy from us or anyone else, dwarf cichlids reward a careful buyer. These are the welfare markers I check:

• The right silhouette. Confirm it's actually agassizii — low even dorsal, spade tail — and not a mislabelled cockatoo or another apisto ^[4]. Trade names are loose; the fin shape isn't.
• Good body condition, not a sunken belly. A hollow stomach or pinched look behind the head suggests a fish that's been underfed or is carrying internal parasites — common in wild imports that haven't settled.
• Clear eyes, intact fins, no white film. Clamped fins and a fish hanging listlessly in a corner are red flags in a species that should be alert and territory-aware.
• Ask about locality or line. Because agassizii is a species complex ^[3], a seller who can tell you whether the fish are a named ornamental line or a specific wild locality is a seller who knows their stock — and it matters enormously if you plan to breed.

Community & clubs

Dwarf cichlids have a devoted following, and the depth of knowledge in the hobby far outstrips any single care sheet — especially for a fish as genetically tangled as agassizii:

• The British Cichlid Association (BCA) is the UK society for cichlid keepers, running talks, a members' journal and shows where you can meet experienced Apistogramma breeders and source healthy, properly-labelled fish (britishcichlid.org).
• apistogramma.com is the long-running international hub for the genus — species profiles, locality discussion and an active forum where keepers trade notes on exactly the kind of line-vs-locality questions that the recent genetic work has made so important (apistogramma.com).

These are where the rarer wild localities and well-kept lines actually change hands — usually between hobbyists, not off a shop shelf.

When your agassizii arrive: acclimation

Dwarf cichlids are more sensitive to chemistry swings than hardy community fish, and the parameter that matters most here is the move into soft, acidic water — a sudden shift in pH or hardness is the main thing that stresses them. Take it slowly:

1. Float the sealed bag for 15–20 minutes to equalise temperature in a dim, quiet room.
2. Drip-acclimate over 45–60 minutes at one or two drops per second. Agassizii from very soft, acidic transport water need a gentle, gradual introduction to your tank's parameters — roughly double the bag volume before you net out.
3. Net the fish into the tank rather than tipping in the transport water, which is acidic and ammonia-laden after the journey.
4. Have caves and cover in place on day one. A territorial fish that can immediately claim a retreat settles far faster than one dropped into an open tank.
5. Lights off and no feeding for the first 24 hours, then start with a small offering of live or frozen food to draw them out.

Ready for more?

• Learn: our cichlid care guide for the fundamentals of keeping cichlids well, and the cardinal tetra guide for the classic dither shoal that brings a shy apisto out into the open.
• Compare: the Apistogramma genus overview to see where agassizii sits among the dwarf cichlids, the cockatoo apisto guide for its crested cousin, and the German blue ram guide for the other soft-water dwarf cichlid most keepers consider alongside it.
• Shop: browse the South American cichlids hub for the wider dwarf-cichlid range, or the tropical fish for sale hub for everything that thrives in a soft, warm, planted tank.