Flyspeck Hardyhead

Craterocephalus stercusmuscarum

Other
Reviewed by Guidarium Editorial DeskUpdated April 30, 2026

The Flyspeck Hardyhead is an active, slender schooling fish native to the freshwater streams and lakes of Australia. Named for the distinct rows of tiny black dots (resembling fly specks) covering its golden-bronze body, it is a highly peaceful species. They are excellent for community tanks, requiring plenty of swimming space, and offer the unique benefit of constantly grazing on algae and aquatic insects.

Flyspeck Hardyhead At a Glance

Adult Size7 cm
Body ShapeFusiform
Growth RateModerate
TemperamentPeaceful
Water TypeFreshwater Only
Flow PreferenceModerate
Waste OutputLow
StockingSchool of 6+

Flyspeck Hardyhead Tank Requirements

Minimum Volume75 L
Minimum Length60 cm
FlowModerate
Water TypeFreshwater Only
Must-Haves in the Tank
Plants - Densely coveredEstablished Algae (Otocinclus)
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Will Flyspeck Hardyhead fit in your tank?

Care guides tell you what Flyspeck Hardyhead needs, the next question is whether your tank can safely provide it. Test Flyspeck Hardyhead against your tank size, maintenance needs, and the fish you already keep before you buy.

Flyspeck Hardyhead
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Flyspeck Hardyhead Water Parameters

Temperature2228°C
pH68
Hardness515 dGH

Flyspeck Hardyhead Temperament & Compatibility

Aggression LevelPeaceful
1/10
Where They Swim
Surface
Mid-level
Bottom
Stocking Guidelines
Keep at Least6 fish
Max per TankNo limit
Can Live Alone?No — needs a group
Behavior Traits
Hyperactive / Fast SwimmerJumper (Lid Required)

Flyspeck Hardyhead Varieties

Each variety inherits the species defaults above. Only differences are highlighted.

Standard / Unsexed

The typical form sold in aquariums. Must be kept in schools of 6 or more to reduce stress and encourage their natural shoaling behavior.

Same care requirements as the base species

Also known as: Juvenile, Silverside

Male

Males are slightly larger than females and develop a vivid bright yellow or gold lower half during the breeding season (some regional variants develop maroon undersides).

Same care requirements as the base species

Also known as: Breeding Male

Female

Females are slightly smaller, paler, and lack the bright yellow belly of breeding males. They possess a rounder abdomen when carrying eggs.

Differs in 1 trait from base species

Adult Size6 cm

Flyspeck Hardyhead Care Guide Summary

The Flyspeck Hardyhead, scientifically known as Craterocephalus stercusmuscarum, belongs to the Other family group. Adults reach a maximum size of approximately 7 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a low level of biological waste.

To thrive, the Flyspeck Hardyhead requires a freshwater only aquarium with a minimum volume of 75 litres and a tank length of at least 60 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 68 and a general hardness of 515 dGH. A moderate water flow is preferred.

The Flyspeck Hardyhead is a rewarding species to keep, provided its core environmental needs are met. This species is available in 3 varieties: Standard / Unsexed, Male, and Female. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.

Flyspeck Hardyhead Habitat Setup

When setting up an aquarium for the Flyspeck Hardyhead, a moderate water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include an established tank with natural algae growth, as they depend on it as a primary food source and dense planting to provide cover, break sightlines, and reduce stress. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.

Flyspeck Hardyhead Compatibility Notes

Classified as peaceful, the Flyspeck Hardyhead is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.

Who Flyspeck Hardyhead Is Actually For

Flyspeck Hardyhead is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 6. It makes the most sense for a hobbyist who will actually build around its needs, especially plants.

The most common mistake is buying Flyspeck Hardyhead for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.

Flyspeck Hardyhead Recommended Tank Sizes

Standard aquarium sizes that meet the minimum volume and length requirements for Flyspeck Hardyhead.

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Frequently Asked Questions About Flyspeck Hardyhead

How big does Flyspeck Hardyhead get?

Flyspeck Hardyhead (Craterocephalus stercusmuscarum) typically reaches a maximum adult size of approximately 7 cm. They have a fusiform body shape and a moderate growth rate.

What tank size does Flyspeck Hardyhead need?

A minimum aquarium volume of 75 litres and a tank length of at least 60 cm are recommended for Flyspeck Hardyhead. This ensures enough swimming space and helps maintain stable water conditions.

What water parameters does Flyspeck Hardyhead need?

Flyspeck Hardyhead thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 6 and 8, and a general hardness of 5–15 dGH. A moderate water flow is preferred.

Is Flyspeck Hardyhead peaceful or aggressive?

Flyspeck Hardyhead is classified as peaceful with an aggression score of 1 out of 10. They are generally well-suited to peaceful community tanks.

How many Flyspeck Hardyhead should be kept together?

Flyspeck Hardyhead is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.

Does Flyspeck Hardyhead have any special tank requirements?

Yes. Flyspeck Hardyhead benefits from plants - densely covered and established algae (otocinclus) in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.

Does Flyspeck Hardyhead need a lid on the tank?

Yes. Flyspeck Hardyhead is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.

Editorial Review

Guidarium Editorial Desk

Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.

Last reviewed
April 30, 2026
Last updated
April 30, 2026
Issues or corrections?
Contact the editorial team

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