Angelfish Enrichment: The Study Found Group Size Did Not Matter
The same study that found neon tetras do better in tens found no group size effect at all for angelfish. They are cichlids, and cichlids are not shoals.
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Angelfish Enrichment: The Study Found Group Size Did Not Matter
A rare thing in this series: a study that included two species and reached opposite conclusions about them. For everything else about them, see our complete Angelfish care guide.
Saxby and colleagues tested group size in four home aquarium species. Neon tetras did measurably better in groups of ten. For angelfish, there was no evidence of a group size effect at all. They are cichlids rather than shoaling fish, and the shoal-size rules that govern a tetra tank simply do not describe them.
What the Research Actually Says
The study is The effect of group size on the behaviour and welfare of four fish species commonly kept in home aquaria, Saxby, Adams, Snellgrove, Wilson and Sloman, Applied Animal Behaviour Science, 2010. The four species: neon tetras, white cloud mountain minnows, angelfish and tiger barbs.
The authors tracked darting, aggression, shoaling and latency to feed, and found these varied with group size in a species-specific manner. Groups of ten neon tetras and white cloud mountain minnows showed improved welfare, covered in full in our Neon Tetra enrichment guide.
For angelfish, no evidence of a group size effect on welfare was found.
That null result is genuinely useful. It means the number that matters most for a tetra is not the number that matters for an angelfish, and it points the enrichment question somewhere else entirely.
The reason angelfish get treated as shoaling fish is that juveniles are sold in groups and behave like one. Adults do not. A tank stocked on the basis of how six young angelfish behave is a tank that will have a problem in about a year.
Height, Not Length
The defining physical requirement. Angelfish are laterally compressed and very tall, and a standard-profile tank cramps them vertically long before it cramps them horizontally.
A deep tank such as a 55 gallon gives adults room to turn and hold position without their fins touching anything. Height is the dimension to buy. Our tank setup guide covers minimums.
Vertical Structure
They evolved among flooded root systems and vertical stems, and they use the water column in a way flat-bodied swimmers do not.
Tall live planting, upright stems, and driftwood arranged with vertical elements give the tank a structure they can orient to. It also breaks sight lines, which matters for the section below.
Leave open water to swim through. Angelfish want cover and cruising space, not a thicket.
Territory, Which Is the Real Social Item
Since group size is not the lever, territory is. Adults pair off and defend space, and a bonded pair in a community tank will push other fish away from their chosen corner, more so around spawning.
Break the tank into visual zones with planting and wood, so a subordinate fish can get out of sight of a dominant one. Sight lines are what turn ordinary cichlid territoriality into one fish being hounded into a corner.
Either keep a bonded pair, or keep enough fish in a large enough tank that aggression spreads rather than fixing on one individual. Two or three adults in a modest tank is the setup that produces a bullied fish.
Tank Mates, Chosen Carefully
Adult angelfish eat what fits in their mouths, which is why the classic angelfish and neon tetra community so often ends with fewer neons. Cardinal tetras are slightly larger and the usual substitute, covered in our Cardinal Tetra enrichment guide.
Avoid fin nippers in the other direction. Long trailing fins on a slow fish are an invitation to barbs and some tetras, and shredded fins are a route into infection. Our health issues guide covers what follows fin damage.
Feeding
Intelligent, food-motivated cichlids that learn a routine quickly and will beg. Vary the diet, include frozen and live foods, and spread feeding across the tank so slower fish get a share.
Do not feed to the begging. Angelfish are convincing and overfeeding a deep-bodied fish is easy. Our feeding guide covers amounts.
Priority Order
- A tall tank, since height is the constrained dimension
- Vertical structure and broken sight lines
- Tank mates too large to be eaten and unlikely to nip
- A bonded pair, or a group big enough to spread aggression
- Varied diet fed across the tank
- Stable water, changed little and often
- Group size, which the study says is not the thing to optimise here
What Not to Do
Do not apply shoaling advice to a cichlid, since the study found it does not apply. Do not stock on the basis of how juveniles behave. Do not buy a long shallow tank for a tall fish. Do not keep two or three adults in a modest tank and expect the aggression to spread. Do not keep them with fin nippers or with fish small enough to eat. And see our handling guide before moving a pair that has started spawning.
For the rest of their care, see our Angelfish cost guide, feeding guide, and tank setup guide, or browse the rest of our Fish care guide category.
Sources & Further Reading
2 sources
- Saxby A, Adams L, Snellgrove D, Wilson RW and Sloman KA (2010). The effect of group size on the behaviour and welfare of four fish species commonly kept in home aquaria. Applied Animal Behaviour Science 125(3-4): 195-205
- The effects of mixed-species assemblage on the behaviour and welfare of fish held in home aquaria. Applied Animal Behaviour Science
❓ Frequently Asked Questions
Is there research on angelfish welfare?
Yes. Angelfish were one of the four species in Saxby and colleagues' 2010 study of group size in home aquarium fish, alongside neon tetras, white cloud mountain minnows and tiger barbs.
What did it find for angelfish?
No evidence of an effect of group size on angelfish welfare, while the same study found groups of ten improved welfare in neon tetras. The effect was species-specific, and angelfish were the species where it did not appear.
Why would angelfish be different?
They are cichlids, not shoaling fish. Adults form pairs and hold territory, and the social structure that makes a shoal of tetras safer in numbers does not describe them. Group size is simply not the variable that governs their welfare.
So what does matter for angelfish?
Height, territory and tank mates. They are tall, deep-bodied fish that need vertical space, and adult pairs become territorial and will harass other fish, especially around spawning.
Can angelfish be kept with neon tetras?
It is a classic pairing and a risky one. Adult angelfish will eat fish small enough to fit, and neon tetras are borderline. Cardinal tetras, being slightly larger, are the usual substitute.
How many angelfish should I keep?
Either a bonded pair, or a group large enough that aggression is spread rather than focused on one fish, in a tank big enough to support it. What does not work is two or three adults in a tank where one gets singled out.
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Written by Michael Ryan
Mike keeps two rescued bearded dragons, Dex and Cera, and writes the care guides on BeastlyFacts from his own research and mistakes. He is not a veterinarian.
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